Check directory handle before we use it

lib/private/tempmanager.php

@@ -132,6 +132,7 @@ class TempManager implements ITempManager {
 		$cutOfTime = time() - 3600;
 		$files = array();
 		$dh = opendir($this->tmpBaseDir);
+		if ($dh) {
 			while (($file = readdir($dh)) !== false) {
 				if (substr($file, 0, 7) === 'oc_tmp_') {
 					$path = $this->tmpBaseDir . '/' . $file;
@@ -141,6 +142,7 @@ class TempManager implements ITempManager {
 					}
 				}
 			}
+		}
 		return $files;
 	}
 }