Fix memory corruption caused by swprintf

[ghost]

swprintf requires a destination buffer size like snprintf. This was previously only working by chance because of how MSVC emits variadic functions.

swprintf also automatically appends a null terminator to the output string so there's no reason to add it via the format string.

This was leading to a buffer overflow and occasional heap corruption.

[Wassimulator]

I've been chasing this. thanks!