Cache: also preserve etags for files

lib/files/cache/scanner.php

@@ -74,8 +74,11 @@ class Scanner {
 					$this->scanFile($parent);
 				}
 			}
-			if ($checkExisting and $data['size'] === -1 and $cacheData = $this->cache->get($file)) {
-				$data['size'] = $cacheData['size'];
+			if ($checkExisting) {
+				$cacheData = $this->cache->get($file)
+				if ($data['size'] === -1) {
+					$data['size'] = $cacheData['size'];
+				}
 				if ($data['mtime'] === $cacheData['mtime']) {
 					$data['etag'] = $cacheData['etag'];
 				}