[FIX] mail: fix traceback when deleting a link preview

This PR fix a traceback that occur when pressing spacebar while the confirm
dialog for deleting a link preview is open.

task-3196494

closes odoo/odoo#113274

X-original-commit: d46a5171378497992bd65634f1aded53db27e9ef
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/models/link_preview_aside_view.js

@@ -11,6 +11,9 @@ Model({
          * Handles the click on delete link preview and open the confirm dialog.
          */
         onClick() {
+            if (!this.exists()) {
+                return;
+            }
             this.update({ linkPreviewDeleteConfirmDialog: {} });
         },
     },