Highlight empty lines
## What does this MR do?
Rather than just highlight the text, file line highlighting now highlights the full line including empty lines
## What are the relevant issue numbers?
Closes#19484
## Screenshots (if relevant)
![Screen_Shot_2016-07-05_at_13.52.31](/uploads/d3bddc918d731681465381e96c0aa2b0/Screen_Shot_2016-07-05_at_13.52.31.png)
See merge request !5092