QtIFW

Don't assert in case of missing dependency

This case is handled anyway, by showing to the user
the message in red.

Change-Id: I64f75901e4fb4fadba255198f5f391d7c2bc1457
Reviewed-by: Niels Weber <niels.weber@digia.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>