It works perfectly fine in single player, yet whenever I'm attempting to get on this modded server I crash. There's a weird thing about it though, if my cursor is not within the boundaries of the game, it goes to the pause screen and I can click the buttons from there. However, once I click on the "Return to game" button, it crashes.
Here is the latest log: https://pastebin.com/efq1yVm9
Once I crash, a message is shown saying "It looks like you are using an unsupported modification of the game"
and
"The game crashed whilst unexpected error
Error: java.lang.NullPointerException: Unexpected error"
I am using Forge 1.7.10 10.13.4.1558.