@ helper's don't work

Nobody has claimed this yet.

Is this nested structure supposed to work?

feed.dust
```
{#activities}
{@select key=category}
{@eq value="event"}{>"views/snapshot/event"/}{/eq}
{/select}
{/activities}
```

event.dust
```

Inside the partial `event` none of the @ helpers function correctly. If I output {counter} or do a context dump the correct value appears. In case it was a type issue I added a string property with a static value and did an @eq test on it which also failed to produce output. {:else} blocks are also not displayed it's as if the entire condition is stripped somehow.

Is this a bug? If I change the @select in the parent view to @eq checks the @ helpers inside `event` do function as you'd expect them to. The reason it's an @select is because there are about 10 different views depending on the value of category.

Start by reproducing the nested @select in feed.dust, the event partial in event.dust, and the comparison where direct @eq checks work. Compare helper and {:else} behavior inside the partial with the parent view, using the shown counter and static string cases. Done means helpers and else blocks render correctly when the partial is selected through @select, with tests covering the nested structure.

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