Adminall spec błąd kompilacji (cannot use 'this' outside of a methodmap method or property)

#include <sourcemod>
#include <dhooks>

#define PLUGIN_VERSION "1.0.2"

new Handle:hIsValidTarget;
new Handle:mp_forcecamera;
new bool:g_bCheckNullPtr = false;

public Plugin:myinfo = 
{
    name = "Admin all spec",
    author = "Dr!fter",
    description = "Allows admin to spec all players",
    version = PLUGIN_VERSION,
    url = "http://www.sourcemod.net"
}

public APLRes:AskPluginLoad2(Handle:myself, bool:late, String:error[], err_max)
{
    MarkNativeAsOptional("DHookIsNullParam");
    
    return APLRes_Success;
}

public OnPluginStart()
{
    mp_forcecamera = FindConVar("mp_forcecamera");
    
    if(!mp_forcecamera)
    {
        SetFailState("Failed to locate mp_forcecamera");
    }
    
    new Handle:temp = LoadGameConfigFile("allow-spec.games");
    
    if(!temp)
    {
        SetFailState("Failed to load allow-spec.games.txt");
    }
    
    new offset = GameConfGetOffset(temp, "IsValidObserverTarget");
    
    hIsValidTarget = DHookCreate(offset, HookType_Entity, ReturnType_Bool, ThisPointer_CBaseEntity, IsValidTarget);
    
    DHookAddParam(hIsValidTarget, HookParamType_CBaseEntity);
    
    CloseHandle(temp);
    
    g_bCheckNullPtr = (GetFeatureStatus(FeatureType_Native, "DHookIsNullParam") == FeatureStatus_Available);
    
    CreateConVar("admin_allspec_version", PLUGIN_VERSION, "Plugin version", FCVAR_PLUGIN|FCVAR_SPONLY|FCVAR_REPLICATED|FCVAR_NOTIFY|FCVAR_DONTRECORD);
}
public OnClientPostAdminCheck(client)
{
    if(IsFakeClient(client))
        return;
    
    if(CheckCommandAccess(client, "admin_allspec_flag", ADMFLAG_CHEATS))
    {
        SendConVarValue(client, mp_forcecamera, "0");
        DHookEntity(hIsValidTarget, true, client);
    }
}
public MRESReturn:IsValidTarget(this, Handle:hReturn, Handle:hParams)
{
    // As of DHooks 1.0.12 we must check for a null param.
    if (g_bCheckNullPtr && DHookIsNullParam(hParams, 1))
        return MRES_Ignored;
    
    new target = DHookGetParam(hParams, 1);
    if(target <= 0 || target > MaxClients || !IsClientInGame(this) || !IsClientInGame(target) || !IsPlayerAlive(target) || IsPlayerAlive(this) || GetClientTeam(this) <= 1 || GetClientTeam(target) <= 1)
    {
        return MRES_Ignored;
    }
    else
    {
        DHookSetReturn(hReturn, true);
        return MRES_Override;
    }
}