While nobody else is on your teams and you do not talk with anyone in Walkie Talkie yet, the page bar and the empty conversations list show Invite someone in place of Start conversation. Before, Start conversation opened a drawer with nobody to choose.
Walkie Talkie offers Invite someone when nobody else is on your teams
When there is nobody you can start a conversation with, Walkie Talkie shows Invite someone in place of Start conversation.