fix(Highcharts plugin): fix updating point x value

[Flunt1k]

A problem arises when the graph has 2 or more series and you need to update the points. When the point.update function is called, the value of x is updated to the index in the flat array.

For example, the graph has 2 series: s1 = [{y: 10}, {y: 15}, {y: 42}], s2 =[{y: null}, {y: 12}, {y: null}], and some categories like ['A', 'B', 'C'].

Before point.update Highcharts has this point representation s1 = [{y: 10, x: 0}, {y: 15, x: 1}, {y: 42, x: 2}], s2 =[{y: null, x: 0}, {y: 12, x: 1}, {y: null, x: 2}]. In this case, x means the index of the category array, I suppose.

Then after updating, the value of the point x changes s1 = [{y: 10, x: 0}, {y: 15, x: 1}, {y: 42, x: 2}], s2 =[{y: null, x: 3}, {y: 12, x: 4}, {y: null, x: 5}].

Highcharts seems to set the index from the merged data as if it were a flat array [{y: 10, x: 0}, {y: 15, x: 1}, {y: 42, x: 2}, {y: null, x: 3}, {y: 12, x: 4}, {y: null, x: 5}].

I added point.x to the update function to save information about the value of x.

[gravity-ui-bot]

Preview is ready.

[Flunt1k]

example https://jsfiddle.net/Flunt1k/p1g493qL