Fix CodeQL error

Author: ikelos

volatility3/cli/volargparse.py

@@ -99,6 +99,7 @@ def _match_argument(self, action, arg_strings_pattern) -> int:
         # return the number of arguments matched
         return len(match.group(1))
 
-    def _check_value(self, action, value):
+    def _check_value(self, action: argparse.Action, value: Any) -> None:
         if not isinstance(action, HelpfulSubparserAction):
             return super()._check_value(action, value)
+        return None