Thread clone segfaults if a class with no fields exists #23771
Description
$ ./perl -Ilib -Mthreads -Mfeature=class -E \
'class X {}; threads->create( sub { say "Hello"; 1 })->join()'
class is experimental at -e line 1.
Segmentation fault
Empty classes do not crash without threads.
Does not crash if you add a field:
$ ./perl -Ilib -Mthreads -Mfeature=class -E 'class X { field $y; }; threads->create( sub { say "Hello"; 1 })->join()'
class is experimental at -e line 1.
field is experimental at -e line 1.
Hello