Check if There is a View Before Checking the Doc

Summary:
This triggers a crash if there is no document open at the moment
something is added to or removed from the project.

Test Plan:
Close all documents and add something to the current
project.

Reviewers: Kile, mludwig

Reviewed By: Kile, mludwig

Tags: Kile

Differential Revision: https://phabricator.kde.org/D7445