only in patch2:
unchanged:
--- a/workbench_moderation.install
+++ b/workbench_moderation.install
@@ -26,6 +26,8 @@ function workbench_moderation_uninstall() {
   variable_del('workbench_moderation_nodedraft_disabled');
   variable_del('workbench_moderation_per_node_type');
   variable_del('workbench_moderation_show_revision_navigation');
+  variable_del('workbench_moderation_state_published');
+  variable_del('workbench_moderation_state_none');
 
   // Get all node types. Loop through them and delete workbench-related variables.
   $types = node_type_get_types();