java.lang.RuntimeException: No OpenGL context found in the current thread

I don't know why this is happening, but a few months ago Minecraft was working fine (along with the fact that I can't access Realms), now after a few days I opened my launcher to play Minecraft and I got the error "java.lang.RunTimeException: No OpenGL context found in the current thread". I don't understand "no OpenGL context" but what is most important is why this is happening.

It hasn't been fixed to this day.

If anyone can help me, I'll give you a super big thank you.

Edit: Turns out fullscreen was causing the problem, and turning it off via options.txt fixed it. I still don't know how fullscreen crashes the game.

Also, turning on fullscreen in the game gives me another error "java.lang.IllegalStateException: Mouse must be created before you can read events"