WelcomePage: Fix warning if searching in examples

During search/filtering the model returns undefined values
for delegates.

Task-number: QTCREATORBUG-11579
Task-number: QTCREATORBUG-11847

Change-Id: Ia15acd54991373f5bdebe4407e4f4a39503f6966
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Help: Use https to access external search engines

Change-Id: I72c1a8de4066cb7532bc6dab64ca70252f0bd05b
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>