Yes, it is OK to set it to `null` because a default label is generated in that case:

```
/**
 * Return symbolic name of a module. This may be generated to a default
 * value or specified in the DSL string.
 *
 * @return module label
 */
public String getModuleLabel() {
	if (moduleLabel == null) {
		return moduleName + "-" + index;
	}
	return moduleLabel;
}
```