It's not clear from your attachment. Presumably the red line is your cell border, even though it appears to be unrelated to the shaded area. That aside, I am guessing that the troublesome line is the thin black one below.

Select both empty paragraphs, open the Borders and Shading dialouge at the bottom of the borders drop-down on the ribbon Home tab (or type ALt+O,B) and remove all borders. That should do it.