fix(pie): cycle stroke.colors across slices instead of indexing off the end

Pie/donut/polarArea data is a single series, so a user-supplied
`stroke.colors` shorter than the slice count was not padded by the theme
engine (unlike fill colors, which already cycle via pushExtraColors). The
per-slice draw indexed `lineColorArr[i]` directly, so only slice 0 got the
requested color and the remaining slices fell back to a grey default —
e.g. `stroke: { colors: ['#fff'] }` left all but the first border grey.

Cycle the array with `lineColorArr[i % length]` so a single color borders
every slice, matching fill-color behaviour. Backward compatible: callers
passing a full-length array still hit `[i]`; an empty array stays undefined.

Author: junedchhipa

src/charts/Pie.js

@@ -303,8 +303,15 @@ class Pie {
 
       const elPath = graphics.drawPath({
         d: path,
+        // Pie/donut/polarArea data is a single series, so a user-supplied
+        // `stroke.colors` shorter than the slice count is NOT padded by the
+        // theme engine (unlike fill colors, which cycle). Without this, only
+        // slice 0 gets the requested color and the rest fall back to a grey
+        // default. Cycle the array — matching fill-color behaviour — so a
+        // single `stroke.colors: ['#fff']` borders every slice as expected.
         stroke: Array.isArray(this.lineColorArr)
-          ? this.lineColorArr[i]
+          ? this.lineColorArr[i] ??
+            this.lineColorArr[i % this.lineColorArr.length]
           : this.lineColorArr,
         strokeWidth: 0,
         fill: pathFill,