use already determined related property (#55075)

we already pull the related model off of the `$query` in the constructor, so we can use it directly.

introduced in #43724

Author: browner12

src/Illuminate/Database/Eloquent/Relations/Relation.php

@@ -172,7 +172,7 @@ abstract public function getResults();
     public function getEager()
     {
         return $this->eagerKeysWereEmpty
-            ? $this->query->getModel()->newCollection()
+            ? $this->related->newCollection()
             : $this->get();
     }