HLDS-SHIELD Help Question (SteamID / Crash)

#include <amxmodx>
#include <amxmisc>
#include <fvault>

#define pluginprefix "[ Tax1r Protection ]"

new const plugininfo[ ][ ] = {
        "anti steam id changer",
        "1.0",
        "Tax1r"
}

new const g_vaultname[ ] = "antisteamidchanger";

new steamidchange_logs[ 54 ];

public plugin_init() {
        register_plugin(plugininfo[ 0 ], plugininfo[ 1 ], plugininfo[ 2 ]);
      
        mkdir("addons/amxmodx/logs/steamidchanger");
        format(steamidchange_logs, charsmax(steamidchange_logs), "addons/amxmodx/logs/steamidchanger/steamidchanger.log", steamidchange_logs);
}

public client_connect(client) {
        new szdata[ 35 ];
        if(fvault_get_data(g_vaultname, user_ip(client), szdata, charsmax(szdata))) {
                loadcmd(client);
                if(!equal(user_authid(client), szdata)) {
                        kickuser(client);
                        return PLUGIN_HANDLED
                }
        }
        else if(!fvault_get_data(g_vaultname, user_ip(client), szdata, charsmax(szdata))) {
                savecmd(client);
                loadcmd(client);
        }
        return PLUGIN_CONTINUE
}

stock kickuser(const index) {
        new szdata[ 35 ];
      
        fvault_get_data(g_vaultname, user_ip(index), szdata, charsmax(szdata));
      
        client_print(index, print_chat, "%s sorry, you have been kicked for using steam id changer.", pluginprefix);
        server_cmd("kick #%d ^"%s steam id change, original steam id : %s.^"", get_user_userid(index), pluginprefix, szdata);
        log_to_file(steamidchange_logs, "%s was kicked, detected steam id change.", user_ip(index));
}

stock user_authid(const index) {
        new authid[ 35 ];
        get_user_authid(index, authid, charsmax(authid));
        return authid;
}

stock user_ip(const index) {
        new ip[ 35 ];
        get_user_ip(index, ip, charsmax(ip), 1);
        return ip;
}

stock savecmd(const index) {
        fvault_set_data(g_vaultname, user_ip(index), user_authid(index));
}

stock loadcmd(const index) {
        fvault_get_data(g_vaultname, user_ip(index), user_authid(index), 34);
    }