Bugfix for issue #46 Deleting folder with Interface files nested underneath, and then saving.
If a tab was open for a certain file and that file was deleted by deleting a parent folder the tab would be kept open. Saving now caused the crash since there was no valid currentDocument any more.
Solution: Close the tab as soon as a file gets deleted by deleted parents.
Merge pull request #306 from NickyWeber/bugfix/issue_46_crash_del_folder_with_ccb_file

Bugfix for issue #46 Deleting folder with Interface files nested underneath, and then saving.