Tooltip "Show all files" crashes VS 2017

### Installed product versions
- Visual Studio: 2017 Enterprise
- This extension: 1.2.71

### Description
VS 2017 crash when trying to see all files from tooltip

### Steps to recreate
1. add a file rule to a .tfignore
2. when the tooltip appears click in "Show all files"

### Current behavior
VS 2017 crashes

### Expected behavior
Don't crash VS 2017 and actually "show all files" 😆 
