When you try to open the chat, a glitched out menu opens in the top right corner of the screen.
  The menu's buttons are covering the exit button, meaning the only way to get back to the game is to close Minecraft completely, and re-open.

  You can't type, you can't choose the preset commands and you can't leave the chat. The only things you can do are change the font of the game's text, change the size of the text, and reset the last two settings. 
  The glitch doesn't occur in worlds created before 1.12, but I've only encountered it in 1.13. (As in, all versions of 1.13. The bug has not yet been resolved with hotfixes.)

I am not the only one to have encountered this issue, as a couple of my friends have also encountered it, the exact same way. Please fix this bug, it renders a lot of functions useless and has gotten in the way numerous times. This isn't crucial, but is incredibly annoying, and never ceases to occur when we open the chat.