fix crash when makeHTTPConnection fails with null pointer

    } else if (!strncasecmp("http://", uri, 7)

            || !strncasecmp("https://", uri, 8)

            || isWidevine) {

        sp<HTTPBase> httpSource = new MediaHTTP(httpService->makeHTTPConnection());

        if (httpService == NULL) {

            ALOGE("Invalid http service!");

            return NULL;

        }

        sp<IMediaHTTPConnection> conn = httpService->makeHTTPConnection();

        if (conn == NULL) {

            ALOGE("Failed to make http connection from http service!");

            return NULL;

        }

        sp<HTTPBase> httpSource = new MediaHTTP(conn);

        String8 tmp;

        if (isWidevine) {