Great! That worked. Although now it's raising another issue. However, this only happens when I try to load up a save from The 1.7.10 pack (where I had all my progress) which has the exact same mods running on it. I can make a new world in my modpack just fine, but I want to play the world with all of my and my friends' progress. Crash report below.
https://pastebin.com/teeEwsBi
Thanks for any help in advance.