SpiderWeb arearange and areasplinerange fill discontinuity

[cromulus]

Expected behaviour

The area range spline should wrap around the spider web chart consistently, connecting the high and low value of each data point on in the range series.

Actual behaviour

the step between the last element in the series and the first element in the series on the spiderweb chart data set, the spline seems to somehow result in a negative value.

The behavior varies between different browsers, which leads me to believe this is not the expected output.

Note: the lines seem to function as expected, it is the area fill that seems to break.

This also breaks with 'arearange' as well.

Live demo with steps to reproduce

http://jsfiddle.net/cromulus/v0r9dtcm/

Affected browser(s)

Chrome: 55.0.2883.95 (64-bit)
Safari: 10.0.2 (12602.3.12.0.1)

[cromulus]

It appears that the same issue is effecting polar arearange charts as well:
http://jsfiddle.net/highcharts/30q95we5/
http://jsfiddle.net/highcharts/30q95we5/

[pawelfus]

Thank you for reporting this issue!

It used to work in 4.2.1: http://jsfiddle.net/v0r9dtcm/7/

Related issue: #5528

[TorsteinHonsi]

It works as expected once we set connectEnds to true: http://jsfiddle.net/v0r9dtcm/8/