MINOR refactor to prevent AttributeError when accessing None (#1914)

* MINOR refactor to prevent AttributeError when accessing None

* Minor fix

* More cleanup

Author: rayokota

src/confluent_kafka/schema_registry/json_schema.py

@@ -565,15 +565,14 @@ def __call__(self, data: bytes, ctx: Optional[SerializationContext] = None) -> U
             if self._registry is not None:
                 writer_schema_raw = self._registry.get_schema(schema_id)
                 writer_schema, writer_ref_registry = self._get_parsed_schema(writer_schema_raw)
+                if subject is None:
+                    subject = self._subject_name_func(ctx, writer_schema.get("title"))
+                    if subject is not None:
+                        latest_schema = self._get_reader_schema(subject)
             else:
                 writer_schema_raw = None
                 writer_schema, writer_ref_registry = None, None
 
-            if subject is None:
-                subject = self._subject_name_func(ctx, writer_schema.get("title"))
-                if subject is not None and self._registry is not None:
-                    latest_schema = self._get_reader_schema(subject)
-
             if latest_schema is not None:
                 migrations = self._get_migrations(subject, writer_schema_raw, latest_schema, None)
                 reader_schema_raw = latest_schema.schema

src/confluent_kafka/schema_registry/protobuf.py

@@ -861,15 +861,14 @@ def __call__(self, data: bytes, ctx: Optional[SerializationContext] = None) -> O
                 fd_proto, pool = self._get_parsed_schema(writer_schema_raw)
                 writer_schema = pool.FindFileByName(fd_proto.name)
                 writer_desc = self._get_message_desc(pool, writer_schema, msg_index)
+                if subject is None:
+                    subject = self._subject_name_func(ctx, writer_desc.full_name)
+                    if subject is not None:
+                        latest_schema = self._get_reader_schema(subject, fmt='serialized')
             else:
                 writer_schema_raw = None
                 writer_schema = None
 
-            if subject is None:
-                subject = self._subject_name_func(ctx, writer_desc.full_name)
-                if subject is not None and self._registry is not None:
-                    latest_schema = self._get_reader_schema(subject, fmt='serialized')
-
             if latest_schema is not None:
                 migrations = self._get_migrations(subject, writer_schema_raw, latest_schema, None)
                 reader_schema_raw = latest_schema.schema