Default to "All" league in character import

[kiwixz]

Description of the problem being solved:

Default to the "All" league in Import/Export Build screen. This is especially useful to allow the character list to preselect the last imported character (saved with a hash).

Steps taken to verify a working solution:

• Import a build in a league other than the first one
• Restart PoB
• Go back to the Import screen
  • Before patch: the first character of the first league would get selected
  • After patch: the character you just imported is preselected

[QuickStick123]

This (#5573) should fix the issue with last imported character not being selected while still having the correct league handled. Since you have looked at this code maybe it will be a good idea to review the linked PR instead.