The sequence that causes the issue:
1. file->row_logging is false because slave-bin was not open;
2. TABLE::mark_columns_per_binlog_row_image() didn't mark column for
read because file->row_logginbg is false. This was implemented in
e53ad95b73 (MDEV-6877);
3. TABLE::update_virtual_fields() didn't update virtual field value
because column is not marked for read;
4. calc_row_difference() sees o_len as UNIV_SQL_NULL, but new row
value is "1". The virtual column is added to update vector;
5. row_upd() tries to update secondary index, but row_upd_sec_step()
doesn't see old value in the index.
The patch does mark_virtual_column_with_deps() via
column_bitmaps_signal() in case of rgi_slave in
mark_columns_per_binlog_row_image() so that non-stored virtual columns
are marked for update in slave thread.
Also fixed column_bitmaps_signal() for partitioning where the signal
did not reach the partition storage engine.
3c38c37432