[ERROR] gamemodes/base/entities/entities/env_skypaint.lua:219: attempt to call method 'SetSunNormal' (a nil value) 1. unknown - gamemodes/base/entities/entities/env_skypaint.lua:219
That error isn't related to the game mode itself as you can see, the error occurs ingamemodes/base/entities/entities/env_skypaint.lua, note the path after the gamemode, it's called "base" which I haven't used or tried on the server, why they're in the leak folder, I wouldn't know as the original leak is by "LovingChild" also stated in the topic.
Anyhow, it's not related to the gamemode itself & I don't use them, as far as I understand the content in the "gamemode" folder in the leak only contains clientsided files and not serversided files, so I highly recommend you only take the SantosRP folder and move it into the gamemodes on your server as that one contains all files needed to run the server