I don't want to steal your post or anything but I'm having the same problem and can't seem to fix it (since it started as the same error I thought I shouldn't make a new thread).
I tried what you guys told OP to do but it didnt do anything/it crashed.
Now, sometimes I don't get the exception error (the guide mentions deleting all .bin files from the /luma/payloads/ folder once you place GodMode9.firm; when I did that I got the exception error but I tried leaving those files and following the rest of the guide which lets me launch the Luma Chainloader menu) and can select SafeB9Installer on Luma Chainloader menu, but all I get is a black screen and it doesn't install. Any ideas?