Dont' create new cell if editing one

Return key is used to change cell line. If cell was in edition, the edition is saved before changing line.

Before this change using return key in the last row, if edited, both saved the change and create new row.

After this change, it'll just save the just, and will need a second key press to create a new row.

I personally think it's better to do one action per key press but I'll be happy counter argument.