fix: prevent error if nativescript.config entry is undefined (#5919)

Author: farfromrefug

lib/commands/config.ts

@@ -38,7 +38,7 @@ export class ConfigListCommand implements ICommand {
 					.join("\n")
 			);
 		} else {
-			return color.yellow(value.toString());
+			return color.yellow(typeof value === 'undefined' ? 'undefined' : value.toString());
 		}
 	}
 }