static instead of self for creating instances

in UploadedFile::loadFilesRecursive
fixes #542

framework/yii/web/UploadedFile.php

@@ -240,7 +240,7 @@ class UploadedFile extends \yii\base\Object
 				self::loadFilesRecursive($key . '[' . $i . ']', $name, $tempNames[$i], $types[$i], $sizes[$i], $errors[$i]);
 			}
 		} else {
-			self::$_files[$key] = new self($names, $tempNames, $types, $sizes, $errors);
+			self::$_files[$key] = new static($names, $tempNames, $types, $sizes, $errors);
 		}
 	}
 }