When going into Full Screen Preview mode by pressing 'F' from the Develop module the text 'No photo selected.' is shown when an adjustment has been made. Undo the the adjustment and press 'F' again. The 'No photo selected.' text is shown again.
Tap the 'G' key to go back to the grid view in the Library module. Tap the 'D' key to go to the Develop module. Tap the 'F' key to go to 'Full Screen Preview' mode. No text is shown this time.
Was happening in Lightroom 5.3 and in 5.4 too. I don't know if this was the case for previous versions. Running on Mac OS X.