chore: default dict for multi query strings too

Signed-off-by: heitorlessa <[email protected]>

Author: heitorlessa

aws_lambda_powertools/utilities/data_classes/api_gateway_proxy_event.py

@@ -115,8 +115,8 @@ def multi_value_headers(self) -> Dict[str, List[str]]:
         return self.get("multiValueHeaders") or {}
 
     @property
-    def multi_value_query_string_parameters(self) -> Optional[Dict[str, List[str]]]:
-        return self.get("multiValueQueryStringParameters")
+    def multi_value_query_string_parameters(self) -> Dict[str, List[str]]:
+        return self.get("multiValueQueryStringParameters") or {}
 
     @property
     def resolved_query_string_parameters(self) -> Dict[str, List[str]]: