Steps to reproduce:
1. Launch GZDoom;
2. Open console by assigned toggleconsole key (grave accent - '`' - in my case).
Note 1: I'm using Dvorak Programming keyboard layout, and actually this key (without Shift) is '$'. For some reason, this key is recognized by GZDoom as grave accent. I wonder if this is related to the problem or not.
3. Close console by using the same key;
Note 2: if the console is closed by Esc key, no crash happens.
First of all, this is not a crash. Try to run Release configuration and "mysteriously" it will go away.
Actually, this is indicated clearly in the log: Assertion 'string != '$'' failed.
As for assertion itself, I think it's wrong. It fails when '$' is entered in console as the first character of a command. Same for menus, chat line, etc.
Most likely, the idea was to catch untranslated text lines. It seems to be impossible to detect such thing correctly there.
About Dvorak keyboard, I have no idea. Could be an issue with SDL or our SDL backend.