Fix an assignment-instead-of-comparison bug. I wish PHP had a better

warning system for this stuff.  In this case it's innocuous because
the UI only allows you to rearrange stuff inside a single album, so
the assignment doesn't do anything.  Fixes #1914.

modules/organize/controllers/organize.php

@@ -154,7 +154,7 @@ class Organize_Controller extends Controller {
       // Move all the source items to the right spots.
       for ($i = 0; $i < count($source_ids); $i++) {
         $source = ORM::factory("item", $source_ids[$i]);
-        if ($source->parent_id = $album->id) {
+        if ($source->parent_id == $album->id) {
           $source->weight = $base_weight + $i;
           $source->save();
         }