Segfault with multiple debuggers open

[AntyMew]

Build: 0.6-4426-d16df697 and 0.1-medusa-4856-8fcf9bee
OS: Debian 9.0 stretch amd64

With both GDB stub and CLI debugger active, sending a command to the CLI debugger segfaults.

Easiest way to reproduce:

• Open CLI debugger
• Break
• Start GDB server
• Send any command to CLI debugger

This does not affect the SDL port, as it will not open if both -d and -g are passed.

[endrift]

hhhh I thought I fixed this. It's supposed to detach the CLI debugger if you start the GDB server.

Anyway this is one of the reasons I haven't released 0.6 yet--the CLI debugger UI isn't well tested yet.