Hi! Love this tool very much. I had issues using this with HTML though and had no idea how to fix it for a while.
Tracked the issue down to the variable; flip_rgb_layout being used as an int while it is a bool. This is normally okay for gamemaker's compiler as it converts it automatically, but when it is converted to javascript it throws an exception.
Changing the bool to a regular integer value seems to fix the issue.
Just a little heads up for anyone wanting to use it with HTML :)