White Edge between photo and border

I've had this happen as well and found 2 things that have helped. 

First, you can use a fill of the same color and that will color the row of transparent pixels. If the border width is an issue see next.

Second, if the border is applied in SL, remove it and export the image. Open it in PS and crop away the transparent rows. Reload and apply the border. That usually gets rid of the blank rows. 

Hope the helps/works.