Fixed #6144, empty categories caused wrong render of tooltip.

js/parts/SvgRenderer.js

@@ -2103,6 +2103,7 @@ SVGRenderer.prototype = {
 			noWrap = textStyles && textStyles.whiteSpace === 'nowrap',
 			fontSize = textStyles && textStyles.fontSize,
 			textCache,
+			isSubsequentLine,
 			i = childNodes.length,
 			tempParent = width && !wrapper.added && this.box,
 			getLineHeight = function (tspan) {
@@ -2238,7 +2239,7 @@ SVGRenderer.prototype = {
 							textNode.appendChild(tspan);
 
 							// first span on subsequent line, add the line height
-							if (!spanNo && lineNo) {
+							if (!spanNo && isSubsequentLine) {
 
 								// allow getting the right offset height in exporting in IE
 								if (!svg && forExport) {
@@ -2317,6 +2318,8 @@ SVGRenderer.prototype = {
 						}
 					}
 				});
+				// To avoid beginning lines that doesn't add to the textNode (#6144)
+				isSubsequentLine = isSubsequentLine || textNode.childNodes.length;
 			});
 
 			if (wasTooLong) {

samples/unit-tests/svgrenderer/text/demo.js

@@ -90,3 +90,25 @@ QUnit.test('textOverflow: ellipsis.', function (assert) {
         'Width was too small for ellipsis.'
     );
 });
+
+QUnit.test('BBox for mulitiple lines', function (assert) {
+    var outerHTML,
+        chart = Highcharts.chart('container', {}, function(chart) {
+            var r = chart.renderer,
+                lab = r.label('<span></span><br/>line<br/>line', 20, 20)
+                    .css({
+                        color: '#f00'
+                    })
+                    .attr({
+                        fill: 'rgba(0, 100, 0, 0.75)',
+                        padding: 0
+                    })
+                    .add();
+            outerHTML = lab.text.element.children[0].outerHTML;
+        });
+
+    assert.ok(
+        !(/dy="\d/.test(outerHTML)),
+        "Frist line shouldn't have dy (#6144) - visually the red text fits in the green box."
+    );
+});