I had the same problem. I called Intuit support and after a lot of back-and-forth they suggested to enter 1 instead of zero in the income and gain columns. They also refused to send me an email with this "advice" so I would have a record of it -- they just sent a link to the CRA explanation for T1135.
After about an hour they dropped the line on me and closed the case.
The problem is (almost certainly) a mistake in the program. It clears out all zero amounts, and then treats these two empty amounts as an error.
If you enter even 0.01 it will stop complaining.
Really incompetent programmers!
