Code could work if "trace" was equal to 0 because it's allowed to pass 0 with get_tr2(), it will retrieve from the global var but when you look at CS code source, it's unlikely.
His code is wrong, forward should be registered as post to be able to retrieve data from trace result. Supposing "trace" is 0, his code would be still wrong because global var is updated once trace line is done.
You can see other people getting a crash in 2009: https://forums.alliedmods.net/showpo...3&postcount=97