Can't join specific realm, just crashes

Summary

What I expected to happen was...:
Open Minecraft, click play and wait for it to load, proceed to Realms and join a specific Realm (owned by TacoBurgerW247) with no problems.

What actually happened was...:
Opened Minecraft as usual, clicked play and waited for it to load. Then I headed to Realms, double clicked the Realm (owned by TacoBurgerW247) it loads terrain, and shows a lighter version of the 'dirt block' background screen waits a second, and shut's itself down with the crash report.

Steps to Reproduce:
1. Grabbed a command block and a button to trigger.
2. Went to heads.freshcoal.com to generate a command for a custom head I had made. I only made the head on the skin, not the body.
3. Put the command into the command block and activated with the button.
4. Minecraft Crashes

Other information:

• Crash report included as attachment
• The owner has deleted me and re-invited me - Still not worked,
• The owner also deleted the command block and the button as well as clearing my inventory, - Still not worked,

Thank you.