Index: sites/all/modules/votingapi/votingapi.module
===================================================================
--- sites/all/modules/votingapi/votingapi.module	(revision 15140)
+++ sites/all/modules/votingapi/votingapi.module	(working copy)
@@ -72,7 +72,7 @@
  *   An array of the votingapi_cache records affected by the vote.
  */
 function votingapi_set_vote($content_type, $content_id, $vote, $uid = NULL, $recursion = FALSE) {
-  if ($uid == NULL) {
+  if (!isset($uid)) {
     global $user;
     $uid = $user->uid;
   }
@@ -130,7 +130,7 @@
  *   The uid of the user casting the vote. If none is specified, the currently logged in user's uid will be inserted.
  */
 function votingapi_unset_vote($content_type, $content_id, $uid = NULL) {
-  if ($uid == NULL) {
+  if (!isset($uid)) {
     global $user;
     $uid = $user->uid;
   }
@@ -172,7 +172,7 @@
  *   The $vote object cast.
  */
 function votingapi_add_vote($content_type, $content_id, $value, $value_type = VOTINGAPI_VALUE_DEFAULT_TYPE, $tag = VOTINGAPI_VALUE_DEFAULT_TAG, $uid = NULL) {
-  if ($uid == NULL) {
+  if (!isset($uid)) {
     global $user;
     $uid = $user->uid;
   }
@@ -305,7 +305,7 @@
  *   An array of matching votingapi_vote records.
  */
 function votingapi_get_user_votes($content_type, $content_id, $uid = NULL) {
-  if ($uid == NULL) {
+  if (!isset($uid)) {
     global $user;
     $uid = $user->uid;
   }