critical check !mat.empty() failed

//when i run my test code getting failed error ? ideas to fix it?

BOOST_AUTO_TEST_CASE(mrz_cnis_fra)
{
std::vector<cv::Point> _v{ { 47, 833 }, { 1510, 836 }, { 1510, 1029 }, { 47, 1023 } };
const cv::Mat mat;
cv::Mat m = cv::imread(image_path("mrz-cnis.jpg").c_str());
BOOST_REQUIRE(!mat.empty());        
idlibrary::mrz::detector d(data_path().c_str());
for (auto i = 0; i < 100; ++i) {
    double a{};
    auto v = d.detect(m, a);
    int x = v.size();
    BOOST_REQUIRE_EQUAL_COLLECTIONS(std::begin(_v), std::end(_v), std::begin(v), std::end(v));

}
}

//error log message

Running 1 test case...
/Users/../test-detector.cpp:78: fatal error in "mrz_cnis": critical check !mat.empty() failed

*** 1 failure detected in test suite "mrz"
Program ended with exit code: 201