what about?

```javascript
var default = trRepoModel.config.wip_limit,
    limits = trRepoModel.config.wip_limits || {};
return limits[this.labelName] || default;
```

This one is really silly but would work
```javascript
return (trRepoModel.config.wip_limits || {})[this.labelName] || trRepoModel.config.wip_limit;
```