Everything was fine but I remembered that there was a mode which only showed the red numbers when necessary. I stopped the game, went to the config folder and changed name = "standard" to name = "minimal".
After the restart and reload of the world I hit the LLOR-Key (F6 in my case) and the game crashed.

MC 1.14.4 Forge 28.0.40 LLOR 1.2.2
https://pastebin.com/XK0CtWj7

Yes that is the case. The crash happened after hitting the LLOR-key but then:
The crash persists. Changing config value back to "standard" or even uninstall the mod:
The world is not playable any more. After one second it crashes with the same NPE and no trace back to LLOR. The only hint I had was the crash after changing the setting to "minimal" and hitting my key. The crash report only shows MC code, as it seems. Please understand that I strongly believe that the minimal mode did st crazy and that the new world I did start now has no LLOR atm.
I even updated Forge to 28.0.41 but no help from that side.

I wish you the very best success in fixing this one.

Thanks. Let me move the light level calculation back to main thread. It should solve this issue if it is cause by LLOR.

This looks to be a different issue related with multithreading. Could you double confirm that it is happening when you are pressing the LLOR-Key? @Knito58

The log shows the crash happened in server chunk thread in minecraft's own code base, and there is no sign of LLOR involving it.

Sorry wanted to check it out but am on Forge 28.0.45 now and the version 1.2.3 of LLOR won't load.

Released 1.2.3

:(
Forge 28.0.45 changed the source code location of tick event (https://files.minecraftforge.net/maven/net/minecraftforge/forge/1.14.4-28.0.45/forge-1.14.4-28.0.45-changelog.txt).

Let compile the code again use the newest Forge.

Can confirm bug gone :)