Is the background behind the spreadsheet solid? If so, an easy way around this would be to have the 'empty' line with actual text and have the text be the same color as the background.
For instance, in your 'empty' line, insert some HTML text like this:
If the background is white as well, then it will appear that this line is empty on the Display. Adjust the color and the text to suit your needs (have text that contains a similar or fewer number of characters).
That worked great. Is there also a way to do something similar at the beginning and/or end of the data? Our spreadsheet scrolls and it is nice to have a separator between. I tried the code you suggested; however, it didn't seem to work.