Clicking 'Edit Project' without a project open make VS sad

### Installed product versions
- Visual Studio: Pro 2017
- This extension: 2.5.0

### Description
Clicking 'Edit Project' without a project open make VS sad

### Steps to recreate
1. Open VS
2. Click **Edit Project**
3. Done

### Current behavior
Presents me with a box saying problem

### Expected behavior
Don't let me do the bad thing