L.Evented.listens() returns false on removed event handlers, #4474 (#4476)

* Fix L.Evented.listens() on removed event handlers, #4474

* Fix bad unit tests for marker events

* Only check for listerners.length if listerners is actually defined

spec/suites/core/EventsSpec.js

@@ -424,4 +424,42 @@ describe('Events', function () {
 			expect(spy2.callCount).to.be(2);
 		});
 	});
+
+	describe('#listens', function () {
+		it('is false if there is no event handler', function () {
+			var obj = new L.Evented(),
+			    spy = sinon.spy();
+
+			expect(obj.listens('test')).to.be(false);
+		});
+
+		it('is true if there is an event handler', function () {
+			var obj = new L.Evented(),
+			    spy = sinon.spy();
+
+			obj.on('test', spy);
+			expect(obj.listens('test')).to.be(true);
+		});
+
+		it('is false if event handler has been removed', function () {
+			var obj = new L.Evented(),
+			    spy = sinon.spy();
+
+			obj.on('test', spy);
+			obj.off('test', spy);
+			expect(obj.listens('test')).to.be(false);
+		});
+
+		it('changes for a "once" handler', function () {
+			var obj = new L.Evented(),
+			    spy = sinon.spy();
+
+			obj.once('test', spy);
+			expect(obj.listens('test')).to.be(true);
+
+			obj.fire('test');
+			expect(obj.listens('test')).to.be(false);
+		});
+	});
+
 });

spec/suites/layer/marker/MarkerSpec.js

@@ -287,17 +287,19 @@ describe("Marker", function () {
 			expect(mapSpy.called).not.to.be.ok();
 		});
 
-		it("do not catch event if it does not listen to it", function () {
+		it("do not catch event if it does not listen to it", function (done) {
 			var marker = new L.Marker([55, 37]);
 			map.addLayer(marker);
 			marker.once('mousemove', function (e) {
 				// It should be the marker coordinates
-				expect(e.latlng).to.be.nearLatLng(marker.getLatLng());
+				expect(e.latlng.equals(marker.getLatLng())).to.be.equal(true);
 			});
 			happen.mousemove(marker._icon);
+
 			map.once('mousemove', function (e) {
 				// It should be the mouse coordinates, not the marker ones
-				expect(e.latlng).not.to.be.nearLatLng(marker.getLatLng());
+				expect(e.latlng.equals(marker.getLatLng())).to.be.equal(false);
+				done();
 			});
 			happen.mousemove(marker._icon);
 		});

src/core/Events.js

@@ -169,6 +169,9 @@ L.Evented = L.Class.extend({
 						break;
 					}
 				}
+				if (listeners.length === 0) {
+					delete events[type];
+				}
 			}
 		}