[Bug] The uncover variables shortcut breaks the url input field

# Describe the bug
Using the uncover variables shortcut results in an error: `Render Failure: Cannot read property 'removeChild' of null`, displayed in the url field.
The rest of the application stays responsive

# To Reproduce
use the uncover variables shortcut (alt + shift + u)

# Expected behavior
The application is shows variables

# Desktop
Distributor ID: Ubuntu
Description: Pop!_OS 19.10
Release: 19.10
Codename: eoan
Installation Method: snap
App Version: 7.0.6

# Additional context
I currently have following variables set:
```
{
"test_endpoint": "https://test.XXXXX.com/v1",
"live_endpoint": "https://api.XXXXX.com/v1",
"now": "{% now 'unix', '' %}"
}
```

Reproduce the issue in the desktop app with the reported variables, then trigger the uncover variables shortcut with Alt+Shift+U and observe the URL field. Trace the shortcut and URL-input rendering path; done means variables are shown without a removeChild render failure and the rest of the application remains responsive.

Written by the indexing model from the issue text.