Fix T2334

Author: Dmitry Kuzin (DevExpress)

src/nouislider.js

@@ -5,14 +5,14 @@ function init(Survey) {
     name: "nouislider",
     title: "noUiSlider",
     iconName: "icon-nouislider",
-    widgetIsLoaded: function() {
+    widgetIsLoaded: function () {
       return typeof noUiSlider != "undefined";
     },
-    isFit: function(question) {
+    isFit: function (question) {
       return question.getType() === "nouislider";
     },
     htmlTemplate: "<div></div>",
-    activatedByChanged: function(activatedBy) {
+    activatedByChanged: function (activatedBy) {
       Survey.JsonObject.metaData.addClass("nouislider", [], null, "empty");
       Survey.JsonObject.metaData.addProperties("nouislider", [
         {
@@ -41,7 +41,7 @@ function init(Survey) {
         }
       ]);
     },
-    afterRender: function(question, el) {
+    afterRender: function (question, el) {
       el.style.marginBottom = "60px";
       var slider = noUiSlider.create(el, {
         start: question.value || (question.rangeMin + question.rangeMax) / 2,
@@ -50,7 +50,7 @@ function init(Survey) {
         tooltips: true,
         pips: {
           mode: question.pipsMode || "positions",
-          values: question.pipsValues.map(function(pVal) {
+          values: question.pipsValues.map(function (pVal) {
             return parseInt((pVal.value !== undefined && pVal.value) || pVal);
           }),
           density: question.pipsDensity || 5
@@ -60,10 +60,10 @@ function init(Survey) {
           max: question.rangeMax
         }
       });
-      slider.on("change", function() {
+      slider.on("change", function () {
         question.value = slider.get();
       });
-      var updateValueHandler = function() {
+      var updateValueHandler = function () {
         slider.set(question.value);
       };
       if (question.isReadOnly) {
@@ -72,17 +72,19 @@ function init(Survey) {
       updateValueHandler();
       question.noUiSlider = slider;
       question.valueChangedCallback = updateValueHandler;
-      question.readOnlyChangedCallback = function() {
+      question.readOnlyChangedCallback = function () {
         if (question.isReadOnly) {
           el.setAttribute("disabled", true);
         } else {
           el.removeAttribute("disabled");
         }
       };
     },
-    willUnmount: function(question, el) {
-      question.noUiSlider.destroy();
-      question.noUiSlider = null;
+    willUnmount: function (question, el) {
+      if (!!question.noUiSlider) {
+        question.noUiSlider.destroy();
+        question.noUiSlider = null;
+      }
       question.readOnlyChangedCallback = null;
     }
   };