Removed key for visualizing the mesh tree.

PiperOrigin-RevId: 533126358
Change-Id: Ic63957427bfe37422e4262fe3551d4a25e92ceae

Author: DeepMind

dm_control/viewer/viewer.py

@@ -63,7 +63,7 @@
 _NEXT_LABELING_MODE = user_input.KEY_F7
 _PRINT_CAMERA = user_input.KEY_F11
 _VISUALIZATION_FLAGS = user_input.Range([
-    ord(functions.mjVISSTRING[i][2])
+    ord(functions.mjVISSTRING[i][2]) if functions.mjVISSTRING[i][2] else 0
     for i in range(0, mujoco.mjtVisFlag.mjNVISFLAG)
 ])
 _GEOM_GROUPS = user_input.Range(