If a query contains compounds not in the database and allowMissing=T, it will return NAs in the missing spots if some compounds exist, but will return a zero length data.frame if none of the compounds exist. It should be updated to return an all NAs vector of the query length if none of the queries exist.
If a query contains compounds not in the database and allowMissing=T, it will return NAs in the missing spots if some compounds exist, but will return a zero length data.frame if none of the compounds exist. It should be updated to return an all NAs vector of the query length if none of the queries exist.