Duplicate forum topic created for the same node

This happens when one user has created a new forum topic on a node by using the discuss this! link, but another user viewing the same page has not refreshed his page(which means his discuss this! link still points to ../discuss/new/{nid}), this will create a duplicate forum topic when this user clicks this link.

I fixed it by adding two lines to discussthis.module:

-------------------------------------------
/**
* Create a new forum topic for the given nid, store the correspondence in the db, and return the new topic nid
**/
function _discussthis_new_topic($nid) {
global $user;

++ $topic_nid = _discussthis_get_topic($nid);
++ if ($topic_nid) return $topic_nid;

// load the node, to get its title/details
$node = node_load(array('nid' => $nid));
$type = node_get_types('name', $node);
$tid = _discussthis_get_forum($nid, $node->type);

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Pretty simple, it checks for an existing forum topic for that node before creating a new one.