NullPointerException in IPPPrintService.findCustomMedia()

FULL PRODUCT VERSION :
java version "1.6.0_04"
Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
Java HotSpot(TM) Server VM (build 10.0-b19, mixed mode)
java version "1.5.0_14"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_14-b03)
Java HotSpot(TM) Server VM (build 1.5.0_14-b03, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Suse Linux Enterprice Server 10
output of uname -a:
Linux 2.6.16.21-0.8-bigsmp #1 SMP Mon Jul 3 18:25:39 UTC 2006
i686 i686 i386 GNU/Linux

EXTRA RELEVANT SYSTEM CONFIGURATION :
CUPS version 1.1.23

A DESCRIPTION OF THE PROBLEM :
We are running a java printing application which executes print jobs for
about hundred different clients on about hundred different printers which
are configured in CUPS. During the test phase everything went fine, but
since we started to use the system in production we repeatedly got the
following NullPointerException in
sun.print.IPPPrintService.findCustomMedia().

    java.lang.NullPointerException
            at
sun.print.IPPPrintService.findCustomMedia(IPPPrintService.java:800)
            at sun.print.UnixPrintJob.print(UnixPrintJob.java:328)
            ...

Since Bug ID 6390756 states the same exception, and since this Bug is
claimed to be a duplicate of 4997933 which is fixed in Java 6.0 I tried to
run the system with Java 1.6.0_04. There I got a similar Exception, which
just had different linennumbers, namely:

    java.lang.NullPointerException
            at
sun.print.IPPPrintService.findCustomMedia(IPPPrintService.java:845)
            at sun.print.UnixPrintJob.print(UnixPrintJob.java:328)

It seems that this NullPointerException is only thrown, when our printing
system is on heavy duty (with respect to the number of printouts, not CPU
usage). Since we use our application in production, it started about 2000
to 7000 print jobs per day. About 500 to 2000 of them where terminated
with this NullPointerException.

While reproducing the problem is very hard, I come up with a solution
already. I downloaded the 1.5.0 JDK source and changed the classes
sun.print.IPPPrintService and sun.print.CUPSPrinter as follows. Please
verify the changes and incorporate them in the next versions of 1.5.0 and
1.6.0.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the above given sources and put them in the boot class path (with
java option -Xbootclasspath/p:).

SOURCE
Attached seperatly

REPRODUCIBILITY :
This bug can be reproduced occasionally.

CUSTOMER SUBMITTED WORKAROUND :
Compile the above given sources and put them in the boot class path (with
java option -Xbootclasspath/p:).