The hash was not cleaned up in any case and sometimes a new object
gets allocated at the exact same address.
To avoid leaking hashes in m_objectInstanceHash and to avoid the assert,
we remove any deleted QObject from the hash.
Change-Id: I2697ab2b2430ad47932841fb9c0ef88ffa4cbbb1
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>