[perl #129120] [CONC] in await: Cannot invoke this object (REPR: Null; VMNull)

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# New Ticket Created by  Zoffix Znet 
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On occasion, I get this error when trying to run the bellow program on a 
32-core box:

$ time RAKUDO_MAX_THREADS=40 perl6 foo.p6 
Cannot invoke this object (REPR: Null; VMNull)
  in block <unit> at foo.p6 line 9


sub what-is {
    return $^num.is-prime ?? "$num is prime" !! "$num is not prime";
}

my @results;
for 3¹²³⁴⁵ … 3¹²³⁴⁵+127 -> $n {
    @results.push: start what-is $n;
}
print await @results;