[phone-app] Background of app while on a call should not be associated to unity's background

[Chris Wayne]

Design comment:
The visual intention is that the when the contact avatar is unavailable it will be using a default image- however, this does not indicate the dash background.

We might need to provide a new visual design for no avatar live screen call.
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While on a phone call, the default background is shown, even if the home screen's background has been changed

[Christina Li (christina-li)]

The visual intention is that the when the contact avatar is unavailable it will be using a default image- however, this does not indicate the dash background.

We might need to provide a new visual design for no avatar live screen call.

[Christina Li (christina-li)]

Updated bug description and name to reflect the bug issue

[Christina Li (christina-li)]

Design working on new designs for no avatar cases

[Olga Kemmet (olga-kemmet)]

Due to design changes we do not show an avatar in the live call screen anymore, weather user set one for a contact or not.