Problem at invoking GetPlayerPos

// a struct, which is is being used for the variable b_stream
struct B_STREAM
{
    AMX *amx_ptr;
    // some stuff...
    unsigned int hooked_natives;
    // some stuff...
    AMX_NATIVE
        // some stuff...
        GetPlayerPos
        // some stuff...
        ;
};

// type definition
typedef vector<B_STREAM> B_STREAM_VECTOR;

// variable
B_STREAM_VECTOR b_stream;

// Test native to call it from a PAWN script
cell AMX_NATIVE_CALL AMX_BStreamTest(AMX *amx, cell *params)
{
    vector_foreach(B_STREAM, b_stream, amx_it)
    {
        if(amx_it->amx_ptr != amx) continue;
        float x, y, z;

        // Le native
        GetPlayerPos(amx_it, params[1], x, y, z);

        // Will return NULL on x, y, and z :-(
        logprintf("Pos: X = %.4f; Y = %.4f; Z = %.4f", x, y, z);

        // This part below works, so do not worry about it :-)
        /*float x = -1974.7776f, y = 124.8516f, z = 26.1731f, r = 0.0f, sdistance = 200.0f;
        logprintf("Connected: %d", IsPlayerConnected(amx_it, params[1]));
        logprintf("Player ID %d: Object ID returns %d ", params[1], CreatePlayerObject(amx_it, params[1], 18876, amx_ftoc(x), amx_ftoc(y), amx_ftoc(z), amx_ftoc(r), amx_ftoc(r), amx_ftoc(r), amx_ftoc(sdistance)));*/
        return 1;
    }
    return 0;
}

// My invoke function...
cell GetPlayerPos(B_STREAM_VECTOR::iterator amx_it, cell playerid, float &x, float &y, float &z)
{
    if((amx_it->hooked_natives&0x2) == 0) return 0;
    cell params[5] = {4, playerid, NULL, NULL, NULL}, ret = amx_it->GetPlayerPos(amx_it->amx_ptr, params);

    // returns null...
    x = amx_ctof(params[2]);

    // returns null...
    y = amx_ctof(params[3]);

    // returns null...
    z = amx_ctof(params[4]);

    // Testing its own return value, returns what it should...
    //logprintf("Returns %d; %.4f; %.4f", ret, ret, amx_ctof(ret));
    return ret;
}