Fix NPE with invalid sourceLevel (and tests).

Fixed the testing infrastructure that was passing tests when it
should not.

Fixed a "what is essential is invisible to the eye" kind of bug
in ArgHandlerSourceLevel.

Change-Id: I9838b6a235a5961fb7e04570f12745aa6b674497
(cherry picked from commit 1082c7efbd95bf4d892ed407ec68cf070e610cb3)
5 files changed