Not sure if this has been posted, but I know this only works for IOS.
If you go to the message tab of the facebook app, click "get app for messenger" then go out of the app store and go back into the facebook app and the tab the message should be gone and you should be able to use it like normal from there on out.
If you go to the message tab of the facebook app, click "get app for messenger" then go out of the app store and go back into the facebook app and the tab the message should be gone and you should be able to use it like normal from there on out.