Fix crash when main() is called but not declared (issue #36)
Fix crash when main() is called but not declared (issue #36)

The compiler sets amxhdr->cip to -1 if main() is not declared, so
check for this in GetPublicAddress().

oscar-broman/samp-plugin-jit,oscar-broman/samp-plugin-jit,Zeex/samp-plugin-jit,Zeex/samp-plugin-jit