Check if a renderer has been instantiated.

DeepMind · copybara-github · commit a7922fdbe718 · 2019-10-12T09:23:46.000-07:00
PiperOrigin-RevId: 274353223
Change-Id: I304776825994dcd86a961ae9a6ac1bc973ede0e9
diff --git a/dm_control/viewer/viewer.py b/dm_control/viewer/viewer.py
@@ -226,7 +226,7 @@ def deinitialize(self):
 
   def render(self):
     """Renders the visualized scene."""
-    if self._camera:
+    if self._camera and self._renderer:  # Can be None during env reload.
       scene = self._camera.render(self.perturbation)
       self._render_settings.apply_settings(scene)
       self._renderer.render(self._viewport, scene)
