Fix attachments

Author: rinkp

include/class.forms.php

@@ -3972,12 +3972,14 @@ function uploadAttachment(&$file) {
 
     static function isValidFile($file) {
         // Make sure mime type is valid
-        if (strcasecmp(FileObject::mime_type($file['tmp_name']),
+        if (!empty($file['tmp_name'])
+            && strcasecmp(FileObject::mime_type($file['tmp_name']),
                     $file['type']) !== 0)
             return false;
 
         // Check invalid image hacks
-        if ($file['tmp_name']
+        if (!empty($file['tmp_name'])
+            && $file['tmp_name']
                 && stripos($file['type'], 'image/') === 0
                 && !exif_imagetype($file['tmp_name']))
             return false;