Fix crash when clicking load without a session selected

qtgui/sessiontreecontroller.py

@@ -303,6 +303,7 @@ class SessionTreeController(object):
 
     def _reactSignal_openSelected(self):
         item = self.treeWidget.currentItem()
+        if item:
             self._reactSignal_itemDoubleClicked(item, column=0)
 
     def _reactSignal_newSession(self):