Many people file tax returns, even if they don't have any income to declare. In order to be eligible for certain benefits programs, a tax return is a must.
If you had no income in 2017, simply skip the income section of the return (and any other sections that don't apply to you) and file.
Since your tax situation is quite simple, I'd recommend using TurboTax Free to prepare and file your return. Learn more here: https://turbotax.intuit.ca/personal-tax-software/free-online.jsp