Issue #3433040 by Anybody, Grevil: Do not return empty array in ApiKeyAuth::authenticate()

src/Authentication/Provider/ApiKeyAuth.php

@@ -83,13 +83,15 @@ class ApiKeyAuth implements AuthenticationProviderInterface {
         $account = reset($accounts);
 
         if (isset($account)) {
+          // Authentication successful:
           return $account;
         }
         break;
       }
     }
 
-    return [];
+    // Authentication failed
+    return NULL;
   }
 
   /**