This is not required due to `createFileInfos` always being run before we
get to this point (I believe this was added after the initial code to
check existence was added).
This flow is covered in
`BeatmapImportTests.TestImportThenReimportAfterMissingFiles`, which
still passes with the change.
While this check isn't doing any harm, as I'm going through the flow for
import-skipping, less checks are appreciated.
336df62a1f