Handle case when ejabberd_auth_* says the account exists

src/web/mod_register_web.erl

@@ -598,6 +598,8 @@ unregister_account(Username, Host, Password) ->
 
 get_error_text({error, captcha_non_valid}) ->
     "The captcha you entered is wrong";
+get_error_text({success, exists, _}) ->
+    get_error_text({atomic, exists});
 get_error_text({atomic, exists}) ->
     "The account already exists";
 get_error_text({error, password_incorrect}) ->