Avoid double caching of OgMembership entities.

Fixes #445

src/MembershipManager.php

@@ -94,27 +94,22 @@ public function getMemberships(AccountInterface $user, array $states = [OgMember
     $identifier = implode(':', $identifier);
 
     // Return cached result if it exists.
-    if (isset($this->cache[$identifier])) {
-      return $this->cache[$identifier];
-    }
+    if (!isset($this->cache[$identifier])) {
+      $query = $this->entityTypeManager
+        ->getStorage('og_membership')
+        ->getQuery()
+        ->condition('uid', $user->id());
 
-    $query = $this->entityTypeManager
-      ->getStorage('og_membership')
-      ->getQuery()
-      ->condition('uid', $user->id());
+      if ($states) {
+        $query->condition('state', $states, 'IN');
+      }
 
-    if ($states) {
-      $query->condition('state', $states, 'IN');
+      $this->cache[$identifier] = $query->execute();
     }
 
-    $results = $query->execute();
-
-    /** @var \Drupal\og\Entity\OgMembership[] $memberships */
-    $this->cache[$identifier] = $this->entityTypeManager
+    return $this->entityTypeManager
       ->getStorage('og_membership')
-      ->loadMultiple($results);
-
-    return $this->cache[$identifier];
+      ->loadMultiple($this->cache[$identifier]);
   }
 
   /**