[perl #69756] [BUG] Null PMC access when doing callwith inside a multi method

[Carl Mäsak]

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<masak> rakudo: multi sub f(0) {}; multi sub f($n) { say $n;
callwith($n - 1) }; f(3)
<p6eval> rakudo 54cfe4: OUTPUT«3␤Null PMC access in clone()␤ [...]
* masak submits rakudobug

jnthn++ informs me that the above code is likely not what I want.
Nevertheless, I expected it do produce something a bit less internal
than a Null PMC access error. Seems jnthn did, too.