Merge pull request #13394 from jsferrei/include-stack-offset

Fix #13356, where tooltips do not display individual values on stacked graphs

public/vendor/flot/jquery.flot.js

@@ -1129,7 +1129,7 @@ Licensed under the MIT license.
                     format.push({ x: true, number: true, required: true });
                     format.push({ y: true, number: true, required: true });
 
-                    if (s.bars.show || (s.lines.show && s.lines.fill)) {
+                    if (s.stack || s.bars.show || (s.lines.show && s.lines.fill)) {
                         var autoscale = !!((s.bars.show && s.bars.zero) || (s.lines.show && s.lines.zero));
                         format.push({ y: true, number: true, required: false, defaultValue: 0, autoscale: autoscale });
                         if (s.bars.horizontal) {