Whenever I try to use a Nether portal, either going into or out of the nether, the game crashes. This is with or without shaders.

To Reproduce
Step 1: Make a portal
Step 2: Go in it.
Step 3: ???
Step 4: Crash!

Expected behavior
I expected to go into or out of the nether.

Screenshots
I took a picture of me being stranded atop the nether, but that's in another bug report, and unrelated to this issue, I think. I made the portal below the top layer of bedrock, by the way. Not on it.

Info (please complete the following information):

• Modpack Version: 2.74
• Server or Singleplayer: Singleplayer, with LAN enabled. No way to create the portal otherwise.
• Version the world was created on: 2.73, I believe

Additional context
Add any other context about the problem here and your thoughts about what could have caused it.

Can you test this on a new 2.74 world and see if the issue persists? Also, provide a crash report so we can actually look into it...