1 - Create a new DirXML-Script Policy
2 - Go to Edit XML
3 - Make sure that "Enable XML Editing" is checked
4 - Delete the XML from that window, and paste the one bellow instead:
<comment xml:space="preserve">WorkAround until a patch is released for BUG 432959</comment>
<if-operation mode="case" op="equal">instance</if-operation>
<if-xml-attr name="src-dn" op="not-available"/>
<do-set-xml-attr expression="." name="src-dn">
5 - Hit Ok to save the changes, restart the driver and test.
This error may show up in other versions of IDM if customization of policies happened but were not done correctly.