FULL PRODUCT VERSION :
java version "1.7.0_45"
Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
Java HotSpot(TM) Client VM (build 24.45-b08, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]
(Windows 7 Enterprise SP1)

A DESCRIPTION OF THE PROBLEM :
When a JNLP file that contains an <icon> element with a href attribute pointing to a GIF image is launched, the NullPointerException pasted below appears in the Java Console. When I replace the GIF with a JPEG or PNG image residing in the same location (folder), the exception does NOT appear. This doesn't occur when I launch Web Start from the command line; only when the JNLP file is launched directly (e.g., double-clicked) and Windows automatically determines the program to open it with. Finally, this only occurs when the application files are not already in the Java cache. If they are, I only see these entries in place of the NPE, which I assume are normal.

CacheEntry[http://localhost:8080/studio/studio.jnlp?mac=0&lolang=en&loc=&louser=]: updateAvailable=false,lastModified=Wed Dec 31 16:00:00 PST 1969,length=2706
CacheEntry[http://localhost:8080/studio/resources.jnlp]: updateAvailable=false,lastModified=Wed Dec 31 16:00:00 PST 1969,length=934
CacheEntry[http://localhost:8080/jnlp/admin/resources.jnlp]: updateAvailable=false,lastModified=Wed Dec 31 16:00:00 PST 1969,length=671
CacheEntry[http://localhost:8080/jnlp/common.jnlp]: updateAvailable=false,lastModified=Wed Dec 31 16:00:00 PST 1969,length=2250

Full stack trace of the NPE that appears in the Java Console:

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at com.sun.deploy.ui.DialogTemplate.imageAvailable(Unknown Source)
at com.sun.deploy.ui.DialogTemplate.finalImageAvailable(Unknown Source)
at com.sun.deploy.ui.ImageLoader$2.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Note that this doesn't seem to affect the functionality of the application at all. However, I observed something else that's probably related: when the <icon> href points to a JPEG or PNG image, that image appears on the right side of the Web Start box that indicates application download progress and "Verifying Application", while a GIF doesn't (the Java logo default appears instead).

REGRESSION. Last worked in version 6u43

ADDITIONAL REGRESSION INFORMATION:
java version "1.6.0_33"
Java(TM) SE Runtime Environment (build 1.6.0_33-b03)
Java HotSpot(TM) Client VM (build 20.8-b03, mixed mode, sharing)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Set Java Console to show
2. Completely clear Java cache (temporary files)
3. Launch a valid JNLP file containing an <icon> element (under <information>) whose href points to a valid, existing GIF image. This must be launched automatically by Windows, by double-clicking the file, for example.
4. See the NullPointerException in the Java Console

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Java Console output:

Java Web Start 10.45.2.18
Using JRE version 1.7.0_45-b18 Java HotSpot(TM) Client VM
User home directory = C:\Users\patelron
----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
m: print memory usage
o: trigger logging
p: reload proxy configuration
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
0-5: set trace level to <n>
----------------------------------------------------
Starting APA Process Engine Version 7.5.0
Build number: 0
Autonomy, Inc. (www.cardiff.com)
LBPM Engine Id = '16.98.104.215$1385516316143'
Batching is supported by database
Analyzing Database Schema...
Completed Analyzing Database Schema...OK
  Total Thread pool size: 21
Date estimation enabled.
Begin scanning database: stalled Synchronous Tasks...
Begin scanning database: tasks ready for processing...
Begin scanning database: completed task sub-trees...
INFO ;Successfully joined process engine cluster.;2013-11-26 17:38:36,380;[javawsApplicationMain]

Engine activation complete.

ACTUAL -
Java Console output:

Java Web Start 10.45.2.18
Using JRE version 1.7.0_45-b18 Java HotSpot(TM) Client VM
User home directory = C:\Users\patelron
----------------------------------------------------
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
m: print memory usage
o: trigger logging
p: reload proxy configuration
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
0-5: set trace level to <n>
----------------------------------------------------
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at com.sun.deploy.ui.DialogTemplate.imageAvailable(Unknown Source)
at com.sun.deploy.ui.DialogTemplate.finalImageAvailable(Unknown Source)
at com.sun.deploy.ui.ImageLoader$2.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Starting APA Process Engine Version 7.5.0
Build number: 0
Autonomy, Inc. (www.cardiff.com)
LBPM Engine Id = '16.98.104.215$1385516440466'
Batching is supported by database
Analyzing Database Schema...
Completed Analyzing Database Schema...OK
  Total Thread pool size: 21
Date estimation enabled.
Begin scanning database: stalled Synchronous Tasks...
Begin scanning database: tasks ready for processing...
Begin scanning database: completed task sub-trees...
INFO ;Successfully joined process engine cluster.;2013-11-26 17:40:40,783;[javawsApplicationMain]

Engine activation complete.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at com.sun.deploy.ui.DialogTemplate.imageAvailable(Unknown Source)
at com.sun.deploy.ui.DialogTemplate.finalImageAvailable(Unknown Source)
at com.sun.deploy.ui.ImageLoader$2.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Options:

- Use a Java 1.6.x JRE
- Replace the GIF image with a PNG or JPEG image in the JNLP file
- Launch from the command line, for example:

C:\Program Files (x86)\Java\jre7\bin>javaws.exe http://localhost:8080/studio