GMOD Crashes when joining a new server.

My GMOD will just crash if I try to join a new DarkRP server and it’s getting really frustrating. I’m able to load into the old server that I used to play on but not any others. I’ve tried re-installing, checking the integrity, and downloading all addons before joining and nothing has worked.
My specs:
iMac (Retina 4k, 21.5-inch, Late 2015)
Processor- 3.1 GHz Intel Core i5
Memory- 8 GB 1867 MHz DDR3
Graphics- Intel Iris Pro Graphics 6200 1536 MB

This is the error that comes up-