FULL PRODUCT VERSION :
C:\Users\pebl>java -version
java version "1.8.0_72"
Java(TM) SE Runtime Environment (build 1.8.0_72-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.72-b15, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
While developing/testing a program, that among other things create images, I had a bug that caused a throwing runtimeexception.
However I also got the following NPE:

Exception in thread "Thread-43" java.lang.NullPointerException
at javax.imageio.stream.FileCacheImageOutputStream.close(FileCacheImageOutputStream.java:229)
at com.sun.imageio.stream.StreamCloser$CloseAction.performAction(StreamCloser.java:130)
at com.sun.imageio.stream.StreamCloser$1.run(StreamCloser.java:74)
at java.lang.Thread.run(Thread.java:745)

I have searched for such bug and I found a 5 year old bug+patch:
http://mail.openjdk.java.net/pipermail/2d-dev/2012-June/002567.html

Looking at the source tells that at least in my java version that I probably hit the same npe.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
This seems like a racy between a throwing a runtimeexception and creating a image in another thread.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Not expecting a NPE.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "Thread-43" java.lang.NullPointerException
at javax.imageio.stream.FileCacheImageOutputStream.close(FileCacheImageOutputStream.java:229)
at com.sun.imageio.stream.StreamCloser$CloseAction.performAction(StreamCloser.java:130)
at com.sun.imageio.stream.StreamCloser$1.run(StreamCloser.java:74)
at java.lang.Thread.run(Thread.java:745)

REPRODUCIBILITY :
This bug can be reproduced rarely.