QUEEN: Switch unknown md5sums in detection entries for NULL.

This tells the advanced detector to skip MD5 validation for this
detection entry, so only filename and size are used as per the
original detection code.
QUEEN: Disable detection entries with unknown MD5sums.

This forces detection of the entries with missing MD5sums via the
fallback detector. This triggers will then trigger a warning
with the associated md5sum for the user to report to the team.