Bug #3210 (and several other possibly related ones) had cases where a recreated database would have these invalid blockset IDs.
It seems like they were caused by filesets referring to a blockset by hash, but not having any index or block file actually containing the block for that hash.
Also fixes countMissingInformation query - it should join with missingBlocklistVolumes, rather than missingBlocklistEntries, as it is selecting the VolumeID.