Bugzilla

With both of these issues an exception is thrown when the selector is clicked for editing. The error message is fixed by bug 1536819.

I suspect that these are both the same issue so I am logging them both in one bug.

### Issue 1 STR

1. Open https://google.co.uk
2. Right-click and inspect the logo.
3. In the rule view click on the `body` selector and change it to something like `booody`.
4. Click somewhere to blur the editor.

A phantom background property appears inside the rule (it doesn't matter what you change the selector to).

### Issue 2 STR

1. Open https://google.co.uk
2. Right-click and inspect the logo.
3. In the rule view click on the `body, html` selector and change it to something like `booody, html`.
4. Click somewhere to blur the editor.
5. Now change the selector back to `body, html`.

The rule becomes dimmed as if it doesn't match anything.

### STR

1. Open https://google.co.uk
2. Right-click and inspect the logo.
3. In the rule view click on the `body` selector and change it to something like `booody`.
4. Click somewhere to blur the editor.

A phantom background property appears inside the rule (it doesn't matter what you change the selector to).