The record doesn't have a valid data snapshot

I add this to test snapshot in my model

public function afterCreate() {

    $changedFields = $this->getChangedFields();
    if (count($changedFields)) {
        foreach ($changedFields as $field) {
            $auditar = new Auditoria();

            $auditar->AUD_MODELNAME = $field;
            $auditar->AUD_IPADRESS = $request->getClientAddress();
            $auditar->AUD_OLDVALUE = $originalData[$field];
            $auditar->save();
            if ($auditar->save() == false) {
                foreach ($auditar->getMessages() as $message) {
                    echo $message, "\n";
                }
            }
        }
    }
}

I add this line to my function initialize

public function initialize() {
    $this->setSchema("SPOLS");
    $this->hasMany('CONT_CODIGO', 'SPMREFERENCIA', 'CONT_CODIGO', array('alias' => 'SPMREFERENCIA'));
    $this->hasMany('CONT_CODIGO', 'SPTDETALLE', 'CONT_CODIGO', array('alias' => 'SPTDETALLE'));
    $this->hasMany('CONT_CODIGO', 'SPTENCABEZADO', 'CONT_CODIGO', array('alias' => 'SPTENCABEZADO'));

    $this->keepSnapshots(true);

}

but when saving me the following message

The record doesn't have a valid data snapshot

Could it be because some fields left empty?