wisteria will crash if a user presses
I (the keybindings that open an external editor to compose a message) without configuring an editor first. Configuring an editor is currently done through modifying the configuration file directly (there's no walkthrough or wizard for it anymore as most users don't want it). This means that most users don't have this keybinding configured and are just waiting to press the wrong key and discover that
We should change things so that we simply log an error indicating that no external editor is configured instead of crashing.