I was playing on my survival world using the latest version of optifine and was flying back to my base to get resources and when I landed I was stuck in flying mode. So I tried a few different solutions such as going into a nether portal or taking my Elytra off but I could not teleport to the nether and when I took my Elytra off I was still in flying mode. At that point I decided to logout, and it has been stuck on the "Saving world" screen ever since. So then I decided to close Minecraft because this same thing had happened earlier, but when I tried closing Minecraft this time, nothing happened. So I ran Task Manager and tried force stopping Minecraft but Minecraft did not appear on Task Manager. So then I opened Minecraft again and tried to reopen the world and it said, "Locked by another running instance of Minecraft" on the "select world" screen. I do not know what else to do and I really don't want to shut the computer down out of fear of corrupting the world. Please help!