Delete a row you added in a piecewise function

How do you delete a row you added in a piecewise function. I was using 2D math input for the piecewise function and I decided not to have the third row at all. Deleting the content of the last row left a space but never removed the entire empty line. Executing it resulted in an error.

The manual only says how to add a row using CTRL + SHIFT + R, but not how to delete a row.

Any advise?