Don't use error suppression on ini_get() either
diff --git a/system/libraries/Upload.php b/system/libraries/Upload.php
index 983d832..4939b15 100644
--- a/system/libraries/Upload.php
+++ b/system/libraries/Upload.php
@@ -1255,7 +1255,7 @@
 				}
 			}
 
-			if ((bool) @ini_get('safe_mode') === FALSE && function_usable('shell_exec'))
+			if ( ! ini_get('safe_mode') && function_usable('shell_exec'))
 			{
 				$mime = @shell_exec($cmd);
 				if (strlen($mime) > 0)