[perl #78276] [BUG] Null PMC access when calling a multi sub with a parameter narrowed by a subtype that does a regex match in Rakudo

[Carl Mäsak via RT]

<tylercurtis> rakudo: multi detect(Str $foo where { /O/ }) {}; detect "O"
<p6eval> rakudo 377615: OUTPUT«Null PMC access in isa_pmc() [...]
<tylercurtis> rakudo: multi detect(Str $foo where /O/) {say 'hi'}; detect "O"
<p6eval> rakudo 377615: OUTPUT«hi␤»
* masak adds this to the ticket
<masak> tylercurtis++
<masak> rakudo: subset G of Str where /O/; multi detect(G) {}; detect "O"; say 
"alive"
<p6eval> rakudo 377615: OUTPUT«alive␤»
<tylercurtis> rakudo: multi detect(Str $foo where { m/O/ } ) {say 'hi'}; detect 
"O"
<p6eval> rakudo 377615: OUTPUT«hi␤»
<masak> another clue. nice!