fix demo

Author: ota-meshi

explorer-v2/build-system/shim/assert.js

@@ -1,4 +1,6 @@
-// eslint-disable-next-line no-undef -- ignore
-module.exports = function () {
-	/* noop */
-};
+if (typeof module !== 'undefined') {
+	// eslint-disable-next-line no-undef -- ignore
+	module.exports = function () {
+		/* noop */
+	};
+}