Set renderer to None

Author: Sam Fries

Packages/vcs/Lib/vtk_ui/manager.py

@@ -79,6 +79,7 @@ def detach(self):
         if self.window.HasRenderer(self.renderer):
             self.window.RemoveRenderer(self.renderer)
         self.renderer.RemoveAllViewProps()
+        self.renderer = None
         self.interactor.RemoveObserver(self.timer_listener)
         self.window.RemoveObserver(self.window_mod)
         self.window.RemoveObserver(self.render_listener)