Fixed a problem leading to CSQC bytecode corruption when autocvars are used.
When a new CSQC program is loaded, pointers to the autocvar globals retain their old values if the corresponding autocvars are not present in the new bytecode. This may lead to CSQC bytecode corruption.
In particular, the problem is prevalent when switching from a RocketMinsta server (which sends an alternative autocvars-enabled CSQC program to clients that support them) to a default Nexuiz server (which doesn't use autocvars).