Fix bug in game master factory that was causing it to rebuild the mem…

…ory on every call to build_game_master, ignoring the optionally provided memory.

PiperOrigin-RevId: 655590212
Change-Id: I332a795a0825bce41fe0998539868264eb98985a

concordia/factory/environment/basic_game_master.py

@@ -86,7 +86,7 @@ def build_game_master(
   Returns:
     A tuple consisting of a game master and its memory.
   """
-  if memory:
+  if memory is not None:
     game_master_memory = memory
   else:
     game_master_memory = associative_memory.AssociativeMemory(