TextMate 2 – recover HTML Output pane

I accidentally dragged the HTML Output split view down below the bottom of the editing pane in TM2, and couldn’t for the life of me get it back. After trawling through the defaults database with no luck, I eventually found the file ~/Library/Application Support/TextMate/Session/Info.plist which contained the value
htmlOutputHeight = -25;

Changing this file seemed to splat the session and I managed to get my markdown preview back.