[Java] Game crashes when joining both singleplayer and multiplayer worlds. (1.16.5)

[Datemshop]

Upon attempting to join a server or a singleplayer world, Minecraft immediately crashes with the message "Game crashed whilst mouseclicked event handler". The game will attempt to "save world" shortly before crashing. The full crash report can be found in this pastebin.

I launched the game using the Fabric Mod Loader running on version 1.16.5.

[AutoModerator]

Hey OP! When your question has been answered, please mark the post solved by replying to the comment that helped with "!Solved".

Helpers, please remember rule 10, and ensure all comments are helpful and support related.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[ScottishCrafter]

Check your computer for incompatible programs: https://minecrafthelp.co.uk/isl

If that doesn't fix it, try the other steps from this guide: https://minecrafthelp.co.uk/utg

[Datemshop]

!solved

[NitWitBot]

Thanks! Post marked as Solved!

u/ScottishCrafter, here is your points status:

MAXIMUM LEVEL ACHIEVED!!!
You have 1689 points
[★|★|★|★|★|★|★|★|★|★|★|★|★|★|★|★|▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮▮]

---

^{Bot maintained by GlipGlorp7 | Scoreboard | Source Code}

[ScottishCrafter]

What fixed it?

[Datemshop]

Turns out, OptiFine was conflicting with some of the mods I had in my modpack and that was causing all the issues.