Merge pull request #76 from ros-visualization/fix_parent_logic

make finding new parent logic more robust

qt_gui/src/qt_gui/dock_widget.py

@@ -136,6 +136,8 @@ def _get_new_parent(self, widget):
         while widget is not None:
             if isinstance(widget, DockableMainWindow):
                 break
+            if not callable(widget.parent):
+                return None
             widget = widget.parent()
         return widget