It is not possible to select object in the popup.php form when using IE 8 browser.

It is not possible to select object in the popup.php form when adding new condition to the action conditions with "Select" option (Host group, Host template, Trigger, etc), as appears error: "length is null or not an object" when using IE7 browser and the latest revision (rev# 20402) from the "trunk" branch.
Please see attached screenshot for more details.