Make a copy of _save_seq to iterate over

Author: jenshnielsen

lib/matplotlib/animation.py

@@ -1084,7 +1084,10 @@ def new_saved_frame_seq(self):
         # no saved frames, generate a new frame sequence and take the first
         # save_count entries in it.
         if self._save_seq:
-            return iter(self._save_seq)
+            # While iterating we are going to update _save_seq
+            # so make a copy to safely iterate over
+            self._old_saved_seq = self._save_seq.copy()
+            return iter(self._old_saved_seq)
         else:
             return itertools.islice(self.new_frame_seq(), self.save_count)