Prevent scrolling for textarea preview (#8472)

prevent scrolling for preview

Prevent that when clicking on preview for a textarea, the page scrolls
to the top and the url changed.

core/src/main/resources/lib/form/textarea/textarea.js

@@ -45,7 +45,8 @@ Behaviour.specify(
     hidePreview.style.display = "none";
     previewDiv.style.display = "none";
 
-    showPreview.onclick = function () {
+    showPreview.onclick = function (event) {
+      event.preventDefault();
       // Several TEXTAREAs may exist if CodeMirror is enabled. The first one has reference to the CodeMirror object.
       var textarea = e.parentNode.getElementsByTagName("TEXTAREA")[0];
       var text = "";
@@ -85,7 +86,8 @@ Behaviour.specify(
       });
     };
 
-    hidePreview.onclick = function () {
+    hidePreview.onclick = function (event) {
+      event.preventDefault();
       hidePreview.style.display = "none";
       previewDiv.style.display = "none";
     };