[FIX] web_editor: prevent traceback when droping undroppable snippet

When trying to drop a snippet that could not be possibly dropped,
a traceback is shown but shouldn't.

Task-2692492

closes odoo/odoo#79924

X-original-commit: 4408dbaf74aa26272b6ed3ce718a2d915975d4b3
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>

addons/web_editor/static/src/js/editor/snippets.editor.js

@@ -2509,7 +2509,9 @@ var SnippetsMenu = Widget.extend({
                         });
                     } else {
                         $toInsert.remove();
-                        dragAndDropResolve();
+                        if (dragAndDropResolve) {
+                            dragAndDropResolve();
+                        }
                         self.$el.find('.oe_snippet_thumbnail').removeClass('o_we_already_dragging');
                     }
                 },