Code that sets a test function up should not be fallible, or should be
designed to log the failure. In tst_moc this is not the case --
QFile::open is called from within a nested lambda. If that fails, print
the error and return an empty optional.
Task-number: QTBUG-123623
Change-Id: I8372a6ac7dc22e68d145fa2215fe04ba682ac81b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>