Fix AttributeError when moving mouse over worldview after closing tab

There is probably something wrong with overloading QWidget.destroy like this. I should rewrite the entire thing in C++ and regain control over object destruction.

src/mcedit2/editorapp.py

@@ -638,12 +638,12 @@ class MCEditApp(QtGui.QApplication):
             if session.closeTab():
                 log.info("Closed session %s", str(session))
                 self.tabWidget.removeTab(index)
-
                 # IMPORTANT: Even after removeTab is called, the tab widget must be unparented
                 tab.setParent(None)
                 self.removeSessionDockWidgets()
                 self.undoGroup.removeStack(session.undoStack)
                 self.sessions.remove(session)
+                session.destroy()
                 gc.collect()
         else:
             self.tabWidget.removeTab(index)

src/mcedit2/editorsession.py

@@ -488,6 +488,13 @@ class EditorSession(QtCore.QObject):
         if hasattr(progress, 'progressCount') and progress.progressCount != progressMax:
             log.info("Update progressMax to %d, please.", progress.progressCount)
 
+    def destroy(self):
+        self.worldEditor.close()
+        self.worldEditor = None
+        self.editorTab.destroy()
+
+        # Break all reference cycles just to be absolutely sure.
+        self.__dict__.clear()
 
     def _updateVersionsAndResourcePacks(self):
         self.mcVersionMapper = QtCore.QSignalMapper()
@@ -1165,14 +1172,9 @@ class EditorSession(QtCore.QObject):
         self.panels = None
 
         self.editorTab.saveState()
-        self.worldEditor.close()
-        self.worldEditor = None
-        # Break all reference cycles just to be absolutely sure.
-        d = {'menus': self.menus, 'undoStack': self.undoStack}
-        self.__dict__.clear()
-        self.__dict__.update(d)
         return True
 
+
     # --- Inspector ---
 
     def inspectBlock(self, pos):
@@ -1314,12 +1316,12 @@ class EditorTab(QtGui.QWidget):
         spacer.setSizePolicy(QtGui.QSizePolicy.Expanding, QtGui.QSizePolicy.Fixed)
         self.viewButtonToolbar.addWidget(spacer)
 
-    def destroy(self):
+    def destroy(self, *a, **kw):
         self.editorSession = None
         for view in self.views:
             view.destroy()
 
-        super(EditorTab, self).destroy()
+        super(EditorTab, self).destroy(*a, **kw)
 
     def setDayTime(self, value):
         if self.editorSession.textureAtlas:

src/mcedit2/worldview/worldview.py

@@ -188,11 +188,11 @@ class WorldView(QGLWidget):
 
         self.setDimension(dimension)
 
-    def destroy(self):
+    def destroy(self, *a, **kw):
         self.makeCurrent()
         self.renderGraph.destroy()
         self.bufferSwapThread.quit()
-        super(WorldView, self).destroy()
+        super(WorldView, self).destroy(*a, **kw)
 
     def __str__(self):
         try: