[FIX] web_editor: avoid error popup when saving incomplete link dialog

Before this commit saving an incomplete link dialog triggered the
display of a stacktrace error popup.

After this commit saving is cancelled when an attempt at saving an
incomplete link dialog is done. The incorrect fields already did display
their error status.

task-2675252

closes odoo/odoo#80043

X-original-commit: 47f0596233c2d8a09d91cdfae117aa3f595bb6bf
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_editor/static/src/js/wysiwyg/widgets/link_dialog.js

@@ -197,6 +197,10 @@ const LinkDialog = Dialog.extend({
      */
     save: function () {
         this.linkWidget.save();
+        if (!this.linkWidget.final_data) {
+            // Invalid form content: do not proceed with save.
+            return;
+        }
         this.final_data = this.linkWidget.final_data;
         return this._super(...arguments);
     },