minor symfony#8949 Update doctrine.rst (MarcusSchwarz)

This PR was merged into the 4.0 branch.

Discussion
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Update doctrine.rst

Fixes two minor issues in code examples

Commits
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4e10bdd Update doctrine.rst

doctrine.rst

@@ -623,7 +623,7 @@ a new method for this to your repository::
             return $qb->execute();
 
             // to get just one result:
-            // $product = $query->setMaxResults(1)->getOneOrNullResult();
+            // $product = $qb->setMaxResults(1)->getOneOrNullResult();
         }
     }
 
@@ -654,6 +654,8 @@ In addition to the query builder, you can also query with `Doctrine Query Langua
 
     public function findAllGreaterThanPrice($price): array
     {
+        $em = $this->getEntityManager();
+        
         $query = $em->createQuery(
             'SELECT p
             FROM App\Entity\Product p