I managed to crash HeidiQSL 22.214.171.12425 with an EAccessViloation by modifying a table and switching from 'Table' to 'Data' view.
Environment: Windows 10, 64-bit talking to MySQL 5.7 on Ubuntu 16.04 LTS server over standard TCP/3306 connection.
I added a new column 'active' (TINYINT) in table view, clicked the data tab to switch to the data view which was displayed but without the new column (I had already been editing data previously).
I expected to right-click and 'Refresh' to see the new column by HeidiSQL threw an error message:
SQL Error (1364): Field 'active' doesn't have a default value
and when I hit 'Ok' it crashed.
Bug report attached.