So I just finalised 3 hours of debugging why I couldn't click a button to trigger a microflow. One of the microflow parameters was purposefully set to optional, but because I set the parameter value on the button to 'empty', the button was disabled. Apparently the parameter value had to be blank/empty, instead of the literally-written value of 'empty'.
Please fix this situation, because the solution had me banging my head against my desk.
Mx10.24.11
This happens because Mendix treats 'empty' (with quotes) as a literal string, not an empty value.
Fix:For optional parameters in a button action, leave the value blank instead of typing 'empty'.
If you type 'empty', Mendix thinks you’re passing the text “empty”, not a null value, so it disables the button (the parameter type doesn’t match).
Blank → passes empty (null) correctly
'empty' (with quotes) → invalid literal string, disables button