radialLinear: fix getIndexAngle when there are no labels (left)

src/controllers/controller.polarArea.js

@@ -1,7 +1,6 @@
 import DatasetController from '../core/core.datasetController';
 import {toRadians, PI} from '../helpers/index';
 import {formatNumber} from '../helpers/helpers.intl';
-import {isNumber} from '../helpers/helpers.math';
 
 export default class PolarAreaController extends DatasetController {
 
@@ -58,11 +57,7 @@ export default class PolarAreaController extends DatasetController {
     const centerX = scale.xCenter;
     const centerY = scale.yCenter;
 
-    if (isNumber(scale.getIndexAngle(0))) {
-      this._lastIndexAngle = scale.getIndexAngle(0);
-    }
-
-    const datasetStartAngle = this._lastIndexAngle - 0.5 * PI;
+    const datasetStartAngle = scale.getIndexAngle(0) - 0.5 * PI;
     let angle = datasetStartAngle;
     let i;
 

src/scales/scale.radialLinear.js

@@ -373,7 +373,9 @@ export default class RadialLinearScale extends LinearScaleBase {
   getIndexAngle(index) {
     const angleMultiplier = TAU / this._pointLabels.length;
     const startAngle = this.options.startAngle || 0;
-    return _normalizeAngle(index * angleMultiplier + toRadians(startAngle));
+    const indexAngle = _normalizeAngle(index * angleMultiplier + toRadians(startAngle));
+
+    return this._pointLabels.length === 0 ? startAngle : indexAngle;
   }
 
   getDistanceFromCenterForValue(value) {