[MAGNAT2645]

I thought so. But anyway thanks for the answers.
But i'm still not sure about using ThrowNativeError inside non-native functions which are called by natives.
Like this:

stock void ThrowNativeErrorIfBadClient(int client, bool inGame = true) {
    if ( client < 1 || client > MaxClients )
        ThrowNativeError( SP_ERROR_NATIVE, "Invalid client index %i", client );

    if ( inGame && !IsClientInGame( client ) )
        ThrowNativeError( SP_ERROR_NATIVE, "Client %i is not in game", client );
}

int NTV_DoSomething(Handle plugin, int numParams) {
    int iClient = GetNativeCell( 1 );
    ThrowNativeErrorIfBadClient( iClient );

    // ...
}