remove duplicate call to groupExists

lib/private/group/manager.php

@@ -76,12 +76,7 @@ class Manager extends PublicEmitter {
 		if (isset($this->cachedGroups[$gid])) {
 			return $this->cachedGroups[$gid];
 		}
-		foreach ($this->backends as $backend) {
-			if ($backend->groupExists($gid)) {
-				return $this->getGroupObject($gid);
-			}
-		}
-		return null;
+		return $this->getGroupObject($gid);
 	}
 
 	protected function getGroupObject($gid) {
@@ -91,6 +86,9 @@ class Manager extends PublicEmitter {
 				$backends[] = $backend;
 			}
 		}
+		if (count($backends) === 0) {
+			return null;
+		}
 		$this->cachedGroups[$gid] = new Group($gid, $backends, $this->userManager, $this);
 		return $this->cachedGroups[$gid];
 	}