[c] Use after free in 4.2 / spine-c

[jabuwu]

I was able to reproduce this crash by loading the provided file in the sfml example: jabuwu/rusty_spine#39

// `repro` is same as `celestialCircus` with animation changed to "idle"
testcase(repro, "", "repro/TGSoT_Character.skel.bytes", "repro/TGSoT_Character.atlas.txt", 1);
// load twice to crash
testcase(repro, "", "repro/TGSoT_Character.skel.bytes", "repro/TGSoT_Character.atlas.txt", 1);

Thanks for your time. Hopefully we can yeet spine-c soon.

[badlogic]

spine-c has been yeeted in 4.3-beta already and replaced with a thin C wrapper around spine-cpp, which should yield better stability.

Thanks for the repro.