BUG: Newlines inserted every time switching back from Source Code Mode

[fyrkantis]

If the last line is empty and selected, an extra newline is inserted before it every time I turn off Source Code Mode, regardless of how many are there already.

A possibly related issue is that turning off Source Code Mode with the last non-empty row selected removes newlines from the end of the file.

I usually switch to and from Source Code Mode a lot to review my changes, which makes this a bit annoying. I'd assume that act of switching between different viewing modes shouldn't change the file in any way.