You are adding some whitespace lines here which we recently removed. I assume you are using FD, which has a really strange behavior in that it keeps whitespace-only lines even if strip whitespaces is set to true.

They fixed it in https://github.com/fdorg/flashdevelop/commit/8b0dcce140a8e9856925ee451ff9d449e4f1ca29, but for the time being we'll have to manually remove these tabs.