Editor is undefined #3033

Describe the bug
The property 'editor' can be undefined (see Screenshots section).

To Reproduce
Steps to reproduce the behavior:

1. Start VSCode
2. Check Breakpoints > Promise Rejects and Breakpoints > Uncaught Exceptions
3. Start my extension in debug mode (Debugger > Launch client). I believe, that can be reproduced with any extension, though it happened to me during development of mine plugin.
4. If any file is opened after start, close all of them and start again.

Expected behavior
The absence of the error.

Screenshots

Environment (please complete the following information):

• Extension (VsCodeVim) version: 0.16.3
• VSCode version: 1.27.1
• OS: Ubuntu 16.04

Additional context

• Probably, that is same as TypeError on empty file #3030.

• Code line I am talking about is src/mode/modeHandler.ts#1324