t2length() doesn't always converge

[Rheeseyb]

I've found that with the below example, the t2length function doesn't converge:
var properties = path.svgPathProperties("M 211.6687111164928,312.6478542077994 C 211.6687111164928,312.6478542077994 211.6687111164928,312.6478542077994 219,293") properties.getPointAtLength(12)

The error value in that function seems to flip flop between 2 values, each time getting slowly closer to the desired error but never quite reaching it, as the delta shrinks with each iteration of the while loop