Merge pull request #971 from UV-CDAT/fix-vcs-exc

Fixes exception from VTKVCSBackend

Looks good thanks

Author: doutriaux1

Packages/vcs/Lib/VTKPlots.py

@@ -54,6 +54,7 @@ def __init__(self,canvas,renWin=None, debug=False,bg=None):
         self.createDefaultInteractor()
     if sys.platform == "darwin":
         self.reRender = False
+    self.clickRenderer = None
 
   def setAnimationStepper( self, stepper ):
       for plot in self.plotApps.values():
@@ -172,9 +173,10 @@ def leftButtonPressEvent(self,obj,event):
     self.renWin.Render()
 
   def leftButtonReleaseEvent(self,obj,event):
-    self.clickRenderer.RemoveAllViewProps()
-    self.renWin.RemoveRenderer(self.clickRenderer)
-    self.renWin.Render()
+    if self.clickRenderer is not None:
+      self.clickRenderer.RemoveAllViewProps()
+      self.renWin.RemoveRenderer(self.clickRenderer)
+      self.renWin.Render()
 
   def configureEvent(self,obj,ev):
     sz = self.renWin.GetSize()