Merge pull request #4792 from heewa/abort-quit-on-failed-save

[Gui] Fix app quitting despite failing to save project

src/Gui/Document.cpp

@@ -1180,6 +1180,7 @@ bool Document::save(void)
         catch (const Base::Exception& e) {
             QMessageBox::critical(getMainWindow(), QObject::tr("Saving document failed"),
                 QString::fromLatin1(e.what()));
+            return false;
         }
         return true;
     }