Call to a member function resolveAssociationEntries() on boolean

The following mistakes occur occasionally:

```
Call to a member function resolveAssociationEntries() on boolean {"detail":"[object] (Symfony\\Component\\Debug\\Exception\\FatalThrowableError(code: 0): Call to a member function resolveAssociationEntries() on boolean at /www/vendor/doctrine/orm/lib/Doctrine/ORM/Cache/DefaultQueryCache.php:140)"}
```

On cache miss the parameter `$entityEntry` sometimes will be false. This fixes issue #7266.

lib/Doctrine/ORM/Cache/DefaultQueryCache.php

@@ -99,7 +99,7 @@ public function get(QueryCacheKey $key, ResultSetMapping $rsm, array $hints = []
         foreach ($cacheEntry->result as $index => $entry) {
             $entityEntry = is_array($entries) ? ($entries[$index] ?? null) : null;
 
-            if ($entityEntry === null) {
+            if (!$entityEntry) {
                 if ($this->cacheLogger !== null) {
                     $this->cacheLogger->entityCacheMiss($regionName, $cacheKeys->identifiers[$index]);
                 }

tests/Doctrine/Tests/ORM/Cache/DefaultQueryCacheTest.php

@@ -344,6 +344,34 @@ public function testGetWithAssociation() : void
         self::assertEquals('Bar', $result[1]->getName());
     }
 
+    public function testGetWithAssociationCacheMiss() : void
+    {
+        $rsm   = new ResultSetMappingBuilder($this->em);
+        $key   = new QueryCacheKey('query.key1', 0);
+        $entry = new QueryCacheEntry(
+            [
+                ['identifier' => ['id' => 1]],
+                ['identifier' => ['id' => 2]],
+            ]
+        );
+
+        $this->region->addReturn('get', $entry);
+
+        $this->region->addReturn(
+            'getMultiple',
+            [
+                new EntityCacheEntry(Country::class, ['id' => 1, 'name' => 'Foo']),
+                false,
+            ]
+        );
+
+        $rsm->addRootEntityFromClassMetadata(Country::class, 'c');
+
+        $result = $this->queryCache->get($key, $rsm);
+
+        self::assertNull($result);
+    }
+
     public function testCancelPutResultIfEntityPutFails() : void
     {
         $result = [];