fix(interaction): Fix null data point interaction

Make sure to filter nullish data when finding closest data points.

Fix #1199

spec/interactions/interaction-spec.js

@@ -1038,4 +1038,68 @@ describe("INTERACTION", () => {
 			}).to.not.throw();
 		});
 	});
+
+	describe("check for bubble null data", () => {
+		before(() => {
+			args = {
+				data: {
+					json: [
+					   {
+						  "x":1,
+						  "b":null,
+						  "a":[1,2]
+					   },
+					   {
+						  "x":2,
+						  "b":null,
+						  "a":[3,1]
+					   },
+					   {
+						  "x":3,
+						  "b":[0,2],
+						  "a":null
+					   },
+					   {
+						  "x":4,
+						  "b":[3,2],
+						  "a":[7,5]
+					   },
+					   {
+						  "x":5,
+						  "b":[5,3],
+						  "a":[2,10]
+					   }
+					],
+					keys: {
+					   "x":"x",
+					   "value":[
+						  "a",
+						  "b"
+					   ]
+					},
+					type: "bubble"
+				}
+			};
+		});
+
+		it("should show tooltip", () => {
+			const point = chart.$.line.circles.filter(v => v.id === "b" && v.index === 2);
+			const r = +point.attr("r");
+
+			// when
+			chart.tooltip.show({
+				mouse: [308.5, 400]
+			});
+
+			chart.$.tooltip.selectAll(".name, .value").each(function() {
+				if (this.classList.contains("name")) {
+					expect(this.textContent).to.be.equal("b");
+				} else if (this.classList.contains("value")) {
+					expect(+this.textContent).to.be.equal(2);
+				}
+			});
+
+			expect(+point.attr("r")).to.be.above(r);
+		});
+	});
 });

src/data/data.js

@@ -628,12 +628,13 @@ extend(ChartInternal.prototype, {
 
 	findClosest(values, pos) {
 		const $$ = this;
+		const data = values.filter(v => v && isValue(v.value));
 		let minDist = $$.config.point_sensitivity;
 		let closest;
 
 		// find mouseovering bar
-		values
-			.filter(v => v && $$.isBarType(v.id))
+		data
+			.filter(v => $$.isBarType(v.id))
 			.forEach(v => {
 				const shape = $$.main.select(`.${CLASS.bars}${$$.getTargetSelectorSuffix(v.id)} .${CLASS.bar}-${v.index}`).node();
 
@@ -643,8 +644,8 @@ extend(ChartInternal.prototype, {
 			});
 
 		// find closest point from non-bar
-		values
-			.filter(v => v && !$$.isBarType(v.id))
+		data
+			.filter(v => !$$.isBarType(v.id))
 			.forEach(v => {
 				const d = $$.dist(v, pos);