Reported with the evidence side by side: a QRZ record plainly carrying
<iota>EU-048</iota>, and no IOTA on the entry.
Adding a field to the lookup cache leaves every row already in it without that
field — and the cache lasts thirty days. So the change worked perfectly for a
callsign never looked up before, and did nothing at all for one already cached,
which is every callsign an operator actually works.
A row written before the column existed has NULL there, and is now treated as
stale: one refetch per such callsign, the next time it is used.
NULL and "" had to be made to mean different things for that. Put no longer
passes the reference through nullable(), so an operator with NO island stores an
empty string — otherwise every ordinary callsign would look unwritten and
refetch for ever, turning a cache into a tax on every lookup. Both halves are
tested.
Same trap for web and zip, added the same way in 0026 and never noticed.
