To prevent an infinite recurison during when a tab is returned (added again) to the original QTabWidget. The recursion was caused by a show event that is emmitted during insert and our QtChatTabs::handleWidgetShown function trying to add the tab again because it is not in the QTabWidget yet; it would be if the show event would be emitted after the insert is done and not somewhere during the insert. Test-Information: Dragging a tab in trellis mode and *not* dropping it on a tab bar. Previously this would cause an infinite recursion. Now it just returns the tab to its previous place. Tested on OS X 10.9.5 with Qt 5.4.0. Change-Id: Icd54b95b6f0542b6a9d3921fa1b0ab4df409950a