Questionmark in header instead of color dot

**Describe the bug**
Questionmark in header instead of color dot

**Steps to reproduce**

1. Open metamask
2. Add custom network like Polygon or BSC
3. Look at dropdown menu on header - questionmark is displayed on the left side of the network name

**Expected behavior**
At least white dot should be displayed as it is in opened drop down menu.
The best would be if user could specify that color when adding new network, this could be even specifying hex color codes.
This might be optional field with default color, if someone could have problem filling it. But when someone fill it then get desired color.
I tried to propose a solution, but unfortunately I have very little js knowledge and as I saw there is plenty code that probably should be change to store new varible.

**Screenshots**

Start by reproducing the custom Polygon or BSC network flow, then trace the header network dropdown and custom-network creation path. Compare the header indicator with the opened dropdown; done means the issue's expected indicator behavior is covered, including the requested custom-color scope if it is accepted.

Written by the indexing model from the issue text.