Fixed #29536 -- Fixed SelectFilter2.js resizing to make boxes have equal height.

Thanks Tim Graham for the review.

django/contrib/admin/static/admin/js/SelectFilter2.js

@@ -164,8 +164,8 @@ Requires jQuery, core.js, and SelectBox.js.
 
             if (!is_stacked) {
                 // In horizontal mode, give the same height to the two boxes.
-                var j_from_box = $(from_box);
-                var j_to_box = $(to_box);
+                var j_from_box = $('#' + field_id + '_from');
+                var j_to_box = $('#' + field_id + '_to');
                 var resize_filters = function() { j_to_box.height($(filter_p).outerHeight() + j_from_box.outerHeight()); };
                 if (j_from_box.outerHeight() > 0) {
                     resize_filters(); // This fieldset is already open. Resize now.

js_tests/admin/SelectFilter2.test.js

@@ -11,6 +11,10 @@ QUnit.test('init', function(assert) {
     SelectFilter.init('id', 'things', 0);
     assert.equal($('.selector-available h2').text().trim(), "Available things");
     assert.equal($('.selector-chosen h2').text().trim(), "Chosen things");
+    assert.equal(
+        $('.selector-available select').outerHeight() + $('.selector-filter').outerHeight(),
+        $('.selector-chosen select').height()
+    );
     assert.equal($('.selector-chooseall').text(), "Choose all");
     assert.equal($('.selector-add').text(), "Choose");
     assert.equal($('.selector-remove').text(), "Remove");