Remove an unnecessary variable initialization
diff --git a/system/libraries/Upload.php b/system/libraries/Upload.php
index fcfd899..a16d5f6 100644
--- a/system/libraries/Upload.php
+++ b/system/libraries/Upload.php
@@ -1020,8 +1020,6 @@
 	 */
 	protected function _file_mime_type($file)
 	{
-		$file_type = '';
-
 		// Use if the Fileinfo extension, if available (only versions above 5.3 support the FILEINFO_MIME_TYPE flag)
 		if ( (float) substr(phpversion(), 0, 3) >= 5.3 && function_exists('finfo_file'))
 		{