Apply suggestions from code review

Also clean up some code, make it less needlessly verbose.

Co-authored-by: Hypolite Petovan <hypolite@mrpetovan.com>

src/Model/User.php

@@ -523,19 +523,18 @@ class User
 		try {
 			$user = self::getAuthenticationInfo($user_info);
 		} catch (Exception $e) {
-			// Addons can create users, and creating a numeric username would create
-			// abiguity with user IDs, possibly opening up an attack vector.
-			// So let's be very careful about that.
-			if (is_numeric($user_info) || is_numeric($user_info['nickname'] ?? '')) {
-				throw $e;
-			}
-
 			$username = (is_string($user_info) ? $user_info : $user_info['nickname'] ?? '');
 
-			if (!$username) {
+			// Addons can create users, and since this 'catch' branch should only
+			// execute if getAuthenticationInfo can't find an existing user, that's
+			// exactly what will happen here. Creating a numeric username would create
+			// abiguity with user IDs, possibly opening up an attack vector.
+			// So let's be very careful about that.
+			if (empty($username) || is_numeric($user_info) || is_numeric($user_info['nickname'] ?? '')) {
 				throw $e;
 			}
-			return self::getIdFromAuthenticateHooks($user_info, $password);
+
+			return self::getIdFromAuthenticateHooks($username, $password);
 		}
 
 		if ($third_party && DI::pConfig()->get($user['uid'], '2fa', 'verified')) {
@@ -582,7 +581,8 @@ class User
 	 * @return int User Id if authentication is successful
 	 * @throws HTTPException\ForbiddenException
 	 */
-	public static function getIdFromAuthenticateHooks($username, $password) {
+	public static function getIdFromAuthenticateHooks($username, $password)
+	{
 		$addon_auth = [
 			'username'      => $username,
 			'password'      => $password,