xdg-mime: actually handle lists in mimeapps.list correctly

The issue was raised in [1]. The earlier fix [2] makes xdg-mime always pick the first item from a list, and that differs from the standard [3].

If the application is no longer installed, the next application in the list is attempted, and so on.

A latter fix [4] implements the standard-compliant behavior, while it does not actually work until [2] is reverted.

[1] https://bugs.freedesktop.org/show_bug.cgi?id=44163

[2] a5ec775d

[3] https://specifications.freedesktop.org/mime-apps-spec/1.0.1/ar01s04.html

[4] 1f8e58d5