At first, I had thought a mod was causing the crash, but after testing each mod individually, every one seemed to make forge crash, forge only loaded with no mods in the mod folder. Forge crashes when it's finished finding modfiles to load.
Minecraft isn't even creating a log for it
I fixed it.. or actually found another way of joining the server. I actually downloaded the version Forge 1.16.5 36.2.0 onto my minecraft folder directly and placed all my mods into the mods file of .minecraft. Thanks for your help and I'm sorry I made you lose your time on me. Have a nice day!
Look at how the glass block is registered, there might be a property for that.
You'll also most likely need to subscribe to FMLClientSetupEvent and then use ItemBlockRenderTypes#setRenderLayer. You'll need to pass it your block and the render type.