mariadb-binlog does not count GEOMETRY rows correctly

mariadb-binlog prints the binary log entry for this statement

INSERT INTO t VALUES

  (ST_GeomFromText('POINT(1 2)')),

  (ST_GeomFromText('POINT(3 4)'));

with

# Number of rows: 1

, no --flashback required.

Code Analysis

The code path uses Rows_log_event::calc_row_event_length() to iterate through a row image.
This method checks both table_def::calc_field_size() and calc_field_event_length() for data validity (even though it only uses calc_field_event_length()'s output).
But calc_field_event_length() does not recognize many data types compared to table_def::calc_field_size() - GEOMETRY beïng one of them, so the 2nd validity check fails, and the counter silently aborts (or emits an error in MDEV-20749) at 1.

Although the duplication between these two functions is technically a separate topic, replacing calc_field_event_length() with table_def::calc_field_size() would fix this issue.
mariadb-binlog --verbose's separate, duplicate (uh) code path that uses only table_def::calc_field_size() proves this, as it is not affected by this issue.