It looks like the do script command in the KM Engine AppleScript Suite would know the resullt, if it runs the macro--which is super--but otherwise it looks the exception. So on the side of safety, if you don't want do script to get the result, specify empty in the text field. To have it both ways, wrap the tell block in an ignoring application response.
ignoring application responses
tell application "Keyboard Maestro Engine"
do script "968B009A-A8F3-4554-839F-2B6B9BBA9CCC"
-- or: do script "return v cancel"
-- or: do script "968B009A-A8F3-4554-839F-2B6B9BBA9CCC" with parameter "Whatever"
end tell
end ignoring