QmlProfiler: fix crash in binding loop detection

The cause of the crash was that animation events are a special case
inside the profile data model, and some parts of the statistics
computation were not taking that circumstance into account.

Change-Id: Ibec929abb18fcdd8af4ddb5ff40b125915746725
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>