[perl #65080] Regex match can cause Null PMC access (in a given / if)

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# New Ticket Created by  Moritz Lenz 
# Please include the string:  [perl #65080]
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08:57 <@moritz_> rakudo: given 'foo' { if /bar/ { 1 } }
08:57 < p6eval> rakudo 9a5305: OUTPUT«Null PMC access in isa_pmc()␤current
                instr.: 'parrot;PGE;Match;new' pc 33
                (compilers/pge/PGE/Match.pir:64)␤»

Funnily when I add a line like this:

lives_ok { given 'foo' { if /bar/ { 1 } } }, 'blubb';

to an existing spectest it passes, so I guess it's something rather
weird, and I don't even know how to test it (until we get qx, of course).

Cheers,
Moritz