Category filter stops working after first context load

The category filter in the inline editor stops functioning when the following steps are taken:

1. Select a context to edit
2. Select a region to add a block (dialog window opens)
3. Select category by which to filter (works as expected)
4. Close dialog window
5. Click 'done' to stop the context from being edited
6. Select a different context to edit
7. Select a region to add a block (dialog window opens)
8. Select category by which to filter (does not work)

The problem is the .click function in initRegions. The previously attached event handler needs to be removed, otherwise each successive attempt to open a new context causes another event to be added.

See the attached patch for review. Thanks.