Fix crash on exit in error reporting

When we get a crash while the application exits (e.g. from the
finalizer method) it's quite possible that the ControlOnUIThread
control already got disposed, so we can't use it anymore.

Change-Id: I93611651663b8afb473063ddf078be8a5a65e682
Merge pull request #126 from ermshiperete/ErrorReporting

Fix crash on exit in error reporting