StagefrightMetadataRetriever: handle error returned from convertMetaDataToMessage().

    sp<MetaData> format = source->getFormat();

    sp<AMessage> videoFormat;

    convertMetaDataToMessage(trackMeta, &videoFormat);

    if (convertMetaDataToMessage(trackMeta, &videoFormat) != OK) {

        ALOGW("Failed to convert meta data to message");

        return NULL;

    }

    // TODO: Use Flexible color instead

    videoFormat->setInt32("color-format", OMX_COLOR_FormatYUV420Planar);