This fixes the following bug:

1) Create two directories (a and b).
2) Open them in tabs in a thunar window.
3) Switch to the tab currently showing a and delete b from a terminal.

Expected behaviour:
Inactive tab showing b will switch to the parent directory.
Active tab showing a will be unaffected.

Actual behaviour:
Inactive tab showing b will switch to the parent directory.
Active tab showing a will not change the directory.