Set keys var otherwise variable not created (#1853)

Author: Andrew-Chen-Wang

redis/commands/parser.py

@@ -103,6 +103,7 @@ def _get_pubsub_keys(self, *args):
             return None
         args = [str_if_bytes(arg) for arg in args]
         command = args[0].upper()
+        keys = None
         if command == "PUBSUB":
             # the second argument is a part of the command name, e.g.
             # ['PUBSUB', 'NUMSUB', 'foo'].
@@ -117,6 +118,4 @@ def _get_pubsub_keys(self, *args):
             # format example:
             # PUBLISH channel message
             keys = [args[1]]
-        else:
-            keys = None
         return keys