The situation happens in force simulations when a point is horribly far (maybe because of a programming error, or because we set the wrong parameters on an experimental force). Then forceCollide calls quadtree(nodes, x,,y), which tries to cover by repeatedly doubling z=0. This ends up crashing the browser.

(rationale: don't let people install @2 in a build system that will not alert them that we have moved to ES6, only to cause trouble with a later release.)