What I want to know is why the hell you would place a tesseract under a Crucible Furnace. Only normal tanks should ever be need to be placed under them. What's annoying about this particular crash, is that it implies, that while the tesseract has a tank, it's not returning it. So just checking if the tanks it returns are null, and if tanks it would return have no fluid is apparently not enough... I'd expect that if it had no tanks you'd return null, rather than an empty array of tanks.
I've come in to so many crashes with TE that I haven't seen from anywhere else... Placing a TE tank next to my sluice, causes a crash, because of the way it handles the sidedness. One second something exists, another it's null. Also fluiducts on the bottom of crucible furnaces cause a 'lucky' crash, if you get lucky in that it detects liquid one second, then the next it's magically gone. (Though I blame this on users, as you shouldn't really be sticking them on the bottom). TE just keeps 'skipping' or changing stuff once it's past my checks. Guess I have to add checks every time, I wanna do anything.
I will fix these quirks when dealing with TE of course in time, it's just annoying .