This is tiny nitpick, but I recommend using False rather than an empty string here (unless there's a reason not to that I'm not seeing). I know empty strings cast to False`, but usingFalse`` explicitly is easier to read.

Small nitpick, but otherwise looks good. Feel free to take or leave my suggestion and merge when ready!

Looks good to me.

@jcline: my reasoning here is that what we would get from the URL's query string is an empty string if the edit mode is off. I always try to have the second argument of .get() be as similar as possible (at least of the same type) as what I would get if there was an actual value.
It comes from a bad experience where I once used .get("arg", False) in a query string and forgot to convert it to boolean, which worked when arg was absent but failed in some cases.

Actually, now that I think of it, I should use the type keyword of args.get()

I'll change that and merge the PR.

@abompard That's a fair argument for the stringy approach and wasn't something I considered. Also, I didn't know about the type keyword either, it looks nice!