Bug fix: Use correct alias lookup method

A regression was introduced during the update to the newer Drupal
version. I accidentally used the wrong alias lookup method, which only
returns true, when what I really wanted was an array of matched paths.

Author: humble-ahitofel

src/AliasGenerator.php

@@ -63,7 +63,7 @@ public function createAllAliases(EntityInterface $entity) {
 
   public function ensureAliasUnique($base, $langcode) {
     $alias = $base;
-    for ($i = 1; $this->aliasRepository->pathHasMatchingAlias($alias, $langcode); $i++) {
+    for ($i = 1; $this->aliasRepository->lookupByAlias($alias, $langcode); $i++) {
       $alias = implode('-', [$base, $i]);
     }
     return $alias;