Fix timeless jewel trade league url

[tbiering]

Fixes #7564 .

Description of the problem being solved:

The "Find Timeless Jewel" function does not properly update the selected league for creation of the trade search url. Details can be found in the bugreport referenced.

Additionally, the window does not restore the last used league when closing and reopening the window.

Steps taken to verify a working solution:

• Manually performed tests
• Manually "broke" the HTTP request for fetching the active leagues in order to test fallback scenarios

Before screenshot:

After screenshot: