How do I turn off the external display screen on my MBP even after I disconnect the second screen?

I connected my MBP to my television via the HDMI port to watch a movie. Whenever I have a second display connected I have different wallpapers for each screen. After the movie was over I disconnected the cable and started surfing the web, and I always have safari full screen so I have to three finger swipe to go back to my desktop. After disconnecting the hdmi cable, the external display screen became part of the three finger swipe in full screen mode. I can swipe to go from safari to second display screen (not connected to anything) and then to my desktop.

My question is how do I get rid of the dog-gone external display screen? I am getting tired of having to swipe more than once from full screen to my desktop.