The Graphics-Card sends the Video-Signal to another Output.
There are some Solutions to avoid this Problem. After a Mission, when you still get a black Screen, please press the "Windows"-Key and "P", after that press "Cursor down" and then "Enter". You may repeat this two or three times, but you should get back your Screen and now you should be able to continue the Game.
Are you playing with an NVIDIA Card? If so, you can change some things in your NVIDIA Control-Panel, to skip this Problem.
Go to "Change Resolution". Scroll down, and please set the Dynamic Output Range from "Limited" to "Full". This helped in my Case, the Problem never appeared again. See the Picture: