Assert in child thread exits without error message?

[FinalEvilution]

I've tested
dmd master 193230b
dmd v2.112.1
ldc    1.42.0
ldc    1.41.0
ldc    1.36.0
ldc    1.32.2
on linux and all of them exit the child thread without an error 
message.

I would think that this is a bug.
But this seems like this has been around for a while and so I'm a 
little confused
as I'd think someone other than me would have tripped over this 
by now.

```d
import std.concurrency;
import std.stdio : writeln;

void main(string[] args)
{
     Tid thread = spawn(&workerThread);
     // assert(false); // This works.
     // User input so this can't be ctfe.
     send(thread, args.length);
     receive((Tid tid) {});
}

void workerThread()
{
     size_t index;

     receive((size_t inIndex) {index = inIndex;});
     writeln("before");

     assert(index == 9999); // This just exits.

     writeln("after");
     send(ownerTid(), thisTid());
}
```