BF: Movie Compon with stopTime=None was trying to calculate stop time

It led to undefine being added to the frameRemains calculation.
Was caused by accidentally altering the contents of the movie params
while trying to convert None->undefined

Don't convert movie.params['stopTime'].val to be undefined!

fixes gh-3182

psychopy/experiment/components/movie/__init__.py

@@ -8,6 +8,7 @@
 from __future__ import absolute_import, print_function
 
 from os import path
+import copy
 from psychopy import logging
 from psychopy.experiment.components import BaseVisualComponent, getInitVals, Param, _translate
 
@@ -150,7 +151,7 @@ def _writeCreationCodeJS(self, buff, useInits):
         if useInits:
             inits = getInitVals(self.params)
         else:
-            inits = self.params
+            inits = copy.deepcopy(self.params)
 
         noAudio = '{}'.format(inits['No audio'].val).lower()
         loop = '{}'.format(inits['loop'].val).lower()