Fixed a crash when casting GN_SPORE_EXPLOSION on certain systems.

- Follow-up to 44c33fda3614d588e6bf6cee1cf884e98f1531f0.
- Also fixed some incorrect va_end calls that came up while debugging.
- Special thanks to Ind for his help debugging the problem.

Signed-off-by: Haru <haru@dotalux.com>