Error reporting can enter infinite loop

[mattrjacobs]

Relevant thread dump:

java.lang.Thread.State: RUNNABLE
at java.lang.Throwable.getCause(Throwable.java:415)
- locked <0x00007f48cf6b4f20> (a java.lang.NullPointerException)
at rx.util.CompositeException.attachCallingThreadStack(CompositeException.java:87)
at rx.util.CompositeException.(CompositeException.java:42)
at rx.util.CompositeException.(CompositeException.java:51)

This is an infinite loop caused by collapsing multiple throwables together. In the presence of CompositeExceptions, we need to break out of the while-loop in CompositeException.attachCallingThreadStack on Throwables that have self-referential loops

[mattrjacobs]

I've got a unit test that duplicates this behavior and a fix. PR coming shortly

[mattrjacobs]

After further review, I still don't have a complete handle on this. The above Pull Request successfully limits the symptom of calling attachCallingThreadStack on a malformed exception, but the malformed exception is still getting created. Since I can't eliminate the malformed exception (yet), I'm submitting a Pull Request that does not call attachCallingThreadStack. This should eliminate the source of the malformed exception, with the loss of informative debugging of CompositeExceptions