Disable Project Export button after deleting preset

(cherry picked from commit 2fc2d82465)

editor/project_export.cpp

@@ -631,6 +631,7 @@ void ProjectExportDialog::_delete_preset_confirm() {
 
 	int idx = presets->get_current();
 	_edit_preset(-1);
+	export_button->set_disabled(true);
 	EditorExport::get_singleton()->remove_export_preset(idx);
 	_update_presets();
 }