support null values for optional int, float fields on save method

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

Author: wiseaidev

aredis_om/model/model.py

@@ -1291,6 +1291,8 @@ async def save(self, pipeline: Optional[Pipeline] = None) -> "HashModel":
             db = pipeline
         document = jsonable_encoder(self.dict())
         # TODO: Wrap any Redis response errors in a custom exception?
+        # store null values as string zero: "0"
+        document = {key: val if val else "0" for key, val in document.items()}
         await db.hset(self.key(), mapping=document)
         return self