Moved CLIENT_ID check in init_app

To prevent the client id from being ignored I moved the check for it to before the check if it is unicode.

flask_mqtt/__init__.py

@@ -105,6 +105,10 @@ def __init__(
 
     def init_app(self, app: Flask) -> None:
         """Init the Flask-MQTT addon."""
+
+        if "MQTT_CLIENT_ID" in app.config:
+            self.client_id = app.config["MQTT_CLIENT_ID"]
+
         if isinstance(self.client_id, unicode):
             self.client._client_id = self.client_id.encode("utf-8")
         else:
@@ -116,9 +120,6 @@ def init_app(self, app: Flask) -> None:
         self.client.on_connect = self._handle_connect
         self.client.on_disconnect = self._handle_disconnect
 
-        if "MQTT_CLIENT_ID" in app.config:
-            self.client_id = app.config["MQTT_CLIENT_ID"]
-
         if "MQTT_CLEAN_SESSION" in app.config:
             self.clean_session = app.config["MQTT_CLEAN_SESSION"]