fix(tooltip): Correct on toggling data series (#253)

Side effect on implementing the new axis.x.tick.tooltip option

Fix #240
Close #253

spec/internals/axis-spec.js

@@ -490,6 +490,9 @@ describe("AXIS", function() {
 					ticks.each(function(d, i) {
 						expect(d3.select(this).select("title").text()).to.be.equal(categories[i]);
 					});
+
+					// check when toggling displaying data series
+					expect(() => chart.hide("data1")).to.not.throw();
 				});
 			});
 

src/axis/bb.axis.js

@@ -399,7 +399,7 @@ export default function(params = {}) {
 			}
 
 			// Append <title> for tooltip display
-			params.tickTitle && textUpdate.append("title")
+			params.tickTitle && textUpdate.append && textUpdate.append("title")
 				.each(function(index) {
 					d3Select(this).text(params.tickTitle[index]);
 				});