When the legend label options are not defined, no error should occur

src/core/core.helpers.js

@@ -964,7 +964,7 @@ module.exports = function(Chart) {
 	};
 	helpers.callback = function(fn, args, thisArg) {
 		if (fn && typeof fn.call === 'function') {
-			fn.apply(thisArg, args);
+			return fn.apply(thisArg, args);
 		}
 	};
 	helpers.getHoverColor = function(colorValue) {

src/plugins/plugin.legend.js

@@ -163,8 +163,8 @@ module.exports = function(Chart) {
 		beforeBuildLabels: noop,
 		buildLabels: function() {
 			var me = this;
-			var labelOpts = me.options.labels;
-			var legendItems = labelOpts.generateLabels.call(me, me.chart);
+			var labelOpts = me.options.labels || {};
+			var legendItems = helpers.callback(labelOpts.generateLabels, [me.chart], me) || [];
 
 			if (labelOpts.filter) {
 				legendItems = legendItems.filter(function(item) {

test/specs/plugin.legend.tests.js

@@ -156,6 +156,31 @@ describe('Legend block tests', function() {
 		}]);
 	});
 
+	it('should not throw when the label options are missing', function() {
+		var makeChart = function() {
+			window.acquireChart({
+				type: 'bar',
+				data: {
+					datasets: [{
+						label: 'dataset1',
+						backgroundColor: '#f31',
+						borderCapStyle: 'butt',
+						borderDash: [2, 2],
+						borderDashOffset: 5.5,
+						data: []
+					}],
+					labels: []
+				},
+				options: {
+					legend: {
+						labels: false,
+					}
+				}
+			});
+		};
+		expect(makeChart).not.toThrow();
+	});
+
 	it('should draw correctly', function() {
 		var chart = window.acquireChart({
 			type: 'bar',