Zero text halo should be no halo

src/stylefunction.js

@@ -1531,7 +1531,7 @@ export function stylefunction(
             ),
             opacity
           );
-          if (haloColor) {
+          if (haloColor && textHaloWidth > 0) {
             textHalo.setColor(haloColor);
             // spec here : https://docs.mapbox.com/mapbox-gl-js/style-spec/#paint-symbol-text-halo-width
             // Halo width must be doubled because it is applied around the center of the text outline

test/stylefunction.test.js

@@ -346,6 +346,25 @@
           done(err);
         });
     });
+
+    it('Zero width text halo should be no halo', function(done){
+      style.layers[0].paint['text-halo-color'] = 'red';
+      style.layers[0].paint['text-halo-width'] = 0;
+      apply(document.createElement('div'), style)
+      .then(function (map) {
+        const layer = map.getLayers().item(0);
+        const styleFunction = layer.getStyle();
+        const feature = layer.getSource().getFeatures()[0];
+        const styles = styleFunction(feature, 1);
+        const text = styles[0].getText();
+        console.log(text.getStroke());
+        should(text.getStroke()).be.undefined();
+        done();
+      })
+      .catch(function (err) {
+        done(err);
+      });
+    });
   });
 
   describe('Declutter mode', function () {