Article fails to load if work item is being edited and changes have been made

[filetrail-dgrossman]

Reproduction steps:

1. Add an instance of this extension to a work item type's definition as a group and correctly link it up to a wiki page URL.
2. Open a work item of that type and collapse the wiki group:
   
3. Open another work item of that type and edit one if its fields. For example, start changing the title.
4. Try to expand the wiki group and observe that it does not populate: