Describe the bug
When I exit a multiplayer sever and then go back to the main menu the whole Main Menu goes into a dark overlay.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Multiplayer'
2. Click on 'a server'
3. Scroll down to 'Exit that server'
4. See error

Expected behavior
It should not be showing as i have no overlay in place that could be causing it

Crash Log
N/A

Screenshots
https://i.imgur.com/35wxo42.png

Basic Informations (please complete the following information):

• OS: Windows
• FancyMenu Version 1.7.1
• Forge Version 14.23.5.2855
• Minecraft Version 1.12.2
• Active Mods OptiFine, and a lot of mods in my modpack i can provide a curseforge zip if required.

Could you provide your modlist? I've been having the same issue and I could narrow down the problem mods based on the mods we have in common.

I did some testing and I figured out that this bug occurs using Fancy Menu 1.7.1, Konkrete 1.1.3, and Forge 14.23.5.2854, and it appears to be an issue with the player entity being rendered on a custom gui. When the game first loads up and I get to the gui with a player entity, there is no dark overlay, but when I enter and exit a world, the gui will have an overlay. The overlay color seems to depend on the brightness in game, as I've tested entering and exiting a world at different times of day, with and without night vision, and with brightness: bright and moody and the results of the overlay change. Here are some screenshots, each labelled with the situation the world was in that I left before they were taken.
Night vision and brightness: bright at night time

No night vision, still using brightness: bright at night time

No night vision, brightness: moody at night time

No night vision, brightness: moody during the day

The overlay only starts existing when I open the custom gui with the player entity on it, but persists when I enter any gui with or without the player entity. The overlay stops when I enter any world. Here are the config files I used:
overworld.txt
overworld.txt
The first is the customguis file, the second is the customization file.

Fixed in FancyMenu v2.0.0! Thank you for your report!