working set does not re-sort when automatic sort is turned on

[joelrbrandt]

steps to reproduce:

1. Add some files to the working set
2. Choose a sorting mode and enable automatic sort
3. Sort an item manually
4. Re-enable automatic sort

expected:

List re-sorts so that it looks the same as after step 2

actual:

List does not change

work around:

Adding another item to the working set triggers a re-sort. Removing an item does not.

[TomMalbran]

Right. Enabling Automatic Sort doesn't trigger an working set sort, but it does make sense that it should. I'll work in a fix for this.