[V4] Using `ensure()` on a task spawned within the current scope raises `Error("halted")`

[cowboyd]

To reproduce, run the code snippet in this discussion #975 (reply in thread)

Expected:

script delays for 2000ms while the sleeping tasks completes.

Actual:

Raises Error("halted")

[13luck]

Faced same issue.

[just-be-dev]

This should be added to the v4 milestone, right?

[cowboyd]

I tested the snippet in #1006 and it worked. Dropping a note here to remember to add a test case for this.