Fix `--threads` argument handling
Fix `--threads` argument handling

beetbox/beets,sampsyo/beets,shamangeorge/beets,shamangeorge/beets,beetbox/beets,shamangeorge/beets,beetbox/beets,ibmibmibm/beets,sampsyo/beets,ibmibmibm/beets,sampsyo/beets,beetbox/beets,shamangeorge/beets,ibmibmibm/beets,ibmibmibm/beets,sampsyo/beets