placeholderPhotoUrl property
The URL of a photo to use if the user's identity does not specify a
photoUrl.
If this is null and the user's identity does not contain a photo URL,
then this widget will attempt to display the user's first initial as
determined from the identity's displayName field. If that is null a
default (generic) Google profile photo will be displayed.
Implementation
final String? placeholderPhotoUrl;