[FIX] web_editor: missing placeholder after saving record

Before this commit:

Creating a new record and saving it afterwards does not show the placeholder in
the description.

After this commit:

You will see placeholders when you create a record and save it.

Task-3167136

X-original-commit: 793e48ae0478ead38ed6ac7c9a71228e2678e2c7
Part-of: odoo/odoo#113811

addons/web_editor/static/src/js/editor/odoo-editor/src/OdooEditor.js

@@ -676,7 +676,8 @@ export class OdooEditor extends EventTarget {
         this._columnUi.remove();
     }
 
-    resetContent(value = '<p><br></p>') {
+    resetContent(value) {
+        value = value || '<p><br></p>';
         this.editable.innerHTML = value;
         this.sanitize();
         this.historyStep(true);