Joining a Minecraft server, and game crashes. No reason why.

Joining a Minecraft server, and game crashes. No reason why.

What I expected to happen was...:
I should join the server and play as per usual.

What actually happened was...:
The second I clicked "Join Server", the game crashed.

Steps to Reproduce:
1. Load game launcher,
2. Click play,
3. Put Minecraft server on list, use the "Add Server" button,
4. Play server,
5. Bug!

Additional notes;

*I have a mac laptop that is 3 yrs old,
*So far the bug has only happened with Mineplex. Could be the graphics causing the bugs. (Sorry, Mineplex.)