JIT: fix carry optimization on blocks that end early

I don't know if this shows up currently, but e.g. if you force blocks to be
under a certain length, this problem (a crash) shows up.
Merge pull request #1773 from FioraAeterna/fixcarryearlyblockend

JIT: fix carry optimization on blocks that end early
Merge branch 'master' of https://github.com/dolphin-emu/dolphin into VR-Hydra