Crash minifying in babili 0.0.12

[AshleyScirra]

Minifying this in babili 0.0.12:

function foo(param)
{
	if (param === null)
		return;
	
	let thingA = param.a;
	let thingB = param.b;
	
	if (!thingA && !thingB)
		return;
	
	let thingC = param.c;
}

crashes with "TypeError: unknown: Cannot read property 'scope' of null".

That's a minimal repro, if you delete any lines from the function foo it doesn't reproduce any more.