Merge pull request #647 from tomcode/patch-1

Zip class checks file exists to prevent error warnings in the log
diff --git a/system/libraries/Zip.php b/system/libraries/Zip.php
index 9101eec..52f1bc3 100644
--- a/system/libraries/Zip.php
+++ b/system/libraries/Zip.php
@@ -99,9 +99,9 @@
 	 */
 	function _get_mod_time($dir)
 	{
-		// filemtime() will return false, but it does raise an error.
-		$date = (@filemtime($dir)) ? filemtime($dir) : getdate($this->now);
-
+		// filemtime() may return false, but raises an error for non-existing files
+		$date = (file_exists($dir)) ? filemtime($dir): getdate($this->now);
+		
 		$time['file_mtime'] = ($date['hours'] << 11) + ($date['minutes'] << 5) + $date['seconds'] / 2;
 		$time['file_mdate'] = (($date['year'] - 1980) << 9) + ($date['mon'] << 5) + $date['mday'];