ios: don't leave the new chat profile picker stuck when the change was cancelled

apiChangeConnectionUser returns nil when the user cancels the Retry
alert, and the picker kept its switching status, so the spinner overlay
stayed and the picker stopped responding. Reset the status and the
selected profile, as the error path does, without the alert.

apps/ios/Shared/Views/NewChat/NewChatView.swift

@@ -477,6 +477,13 @@ private struct ActiveProfilePicker: View {
                                     )
                                 }
                             }
+                        } else {
+                            await MainActor.run {
+                                profileSwitchStatus = .idle
+                                if let currentUser = chatModel.currentUser {
+                                    selectedProfile = currentUser
+                                }
+                            }
                         }
                     } catch {
                         await MainActor.run {