Catch error when a cardset image fails to load

Author: joeraz

pysollib/images.py

@@ -181,6 +181,8 @@ def load(self, app, progress=None):
         # load face cards
         for n in self.cs.getFaceCardNames():
             self._card.append(self.__loadCard(n + self.cs.ext))
+            if self._card[-1] is None:
+                return 0
             self._card[-1].filename = n
             if progress:
                 progress.update(step=pstep)