It returns filing for nri student having no income

My son is studying post grad in Australia from Feb 2017 and continue till Dec 2018. He was totally out of India throughout FY18 hence NRI. He didn't have any income in India or Australia. However, in the previous FY17, he had income from internship and capital gains on equity investments in India hence had filed returns last year.
Question is : Is it necessary to file returns for FY18 even if no income? Especially because his status has changed from Resident to NRI.