JIT keeps a capture returned from an abandoned (*ACCEPT) subroutine attempt #1047

Found while working on #1046. With JIT, a group returned through a capture list ((?&name(N))) can keep the value it had in an attempt of the called group that was later abandoned. Reproducer from @NWilson in #1046:

/^(?:(?&r(2))X|a)(?(2)Y|b)$(?(DEFINE)(?<r>(a)(*ACCEPT)x))/
    ab
    aY

pcre2test output (main at 9b338eb, CMake Release build, JIT on, macOS arm64):

/^(?:(?&r(2))X|a)(?(2)Y|b)$(?(DEFINE)(?<r>(a)(*ACCEPT)x))/jit
    ab
No match
    aY
 0: aY
 1: <unset>
 2: a

The first alternative (?&r(2))X fails (no X after the returned a), so the second alternative a matches and group 2 should be unset at the (?(2)…) condition: ab should match and aY should not. With JIT, group 2 keeps a from the abandoned first alternative.

The interpreter on main fails on this pattern with error -44 (that is what #1046 fixes); with #1046 it matches ab and rejects aY.