TypeError: d.firstChild is null

I am working on a problem that seems to be introduced by a relatively new build of DOMVM, meaning the code used to work without issue. The symptom is the type error in the subject.

I have not gotten to the point of a fiddle yet since I have no clue yet how to replicate the fault outside of the context of my app. All I am looking for at this point is suggestions for the kind of mistake or fault I could make that could cause the firstChild property to be unexpectedly null when patching.

If it helps, it seems to only happen when the display is recreated, but unchanged.

It happens in patch, here:

	else {
		// "" | null => []
		if (newIsArr) {
			clearChildren(donor);
			hydrateBody(vnode);
		}
		// "" | null => "" | null
		else if (nbody !== obody) {
			if (nbody != null && obody != null)
				{ el.firstChild.nodeValue = nbody; } // <== el.firstChild is null
			else
				{ el.textContent = nbody; }
		}
	}

The stacktrace is:

TypeError: el.firstChild is null, can't access property "nodeValue" of it[Learn More] AppScript:1498:8
	patch https://localhost/jse/AppScript:1498:8
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	patchChildren https://localhost/jse/AppScript:1605:7
	patch https://localhost/jse/AppScript:1480:7
	redrawSync https://localhost/jse/AppScript:1916:8
	updateSync https://localhost/jse/AppScript:1942:10
	patchChildren https://localhost/jse/AppScript:1612:7
	patch https://localhost/jse/AppScript:1480:7
	redrawSync https://localhost/jse/AppScript:1916:8
	redraw https://localhost/jse/AppScript:1755:8
	redraw/vm._redrawAsync< https://localhost/jse/AppScript:1757:73
	call https://localhost/jse/AppScript:293:4

[lawrence-dol]

please test it out in your app before i cut a new release.

It works just fine. I measure a 6% performance improvement in Firefox (over 921 redraws).

/* File 7: domvm.micro.min.js */
// https://github.com/domvm/domvm (3.x-dev, micro build)
!function(e,n){"object"==typeof exports&&"undefined"!=typeof module?n(...

[leeoniya]

i added body stringification except for null, Array and List types. all tests still pass. there was no measurable perf impact (in Chrome).

please test it out in your app before i cut a new release.