prepared statements with cursor protocol).
The problem was a bug in Materialized-cursor implementation.
Materialized_cursor::open() called send_result_metadata()
with items pointing to already closed table.
The fix is to send metadata when the table is still open.
NOTE: this is a "partial" fix: metadata are different with
and without --cursor-protocol, but that's a different large
problem, one indication of which is reported as Bug 24176.
ae03e16b24