use orEmpty()

vector/src/main/java/im/vector/app/features/invite/InviteUsersToRoomViewModel.kt

@@ -92,6 +92,6 @@ class InviteUsersToRoomViewModel @AssistedInject constructor(@Assisted
     }
 
     fun getUserIdsOfRoomMembers(): Set<String> {
-        return room.roomSummary()?.otherMemberIds?.toSet() ?: emptySet()
+        return room.roomSummary()?.otherMemberIds?.toSet().orEmpty()
     }
 }

vector/src/main/java/im/vector/app/features/roomdirectory/RoomDirectoryViewModel.kt

@@ -87,7 +87,7 @@ class RoomDirectoryViewModel @AssistedInject constructor(
                     val joinedRoomIds = list
                             ?.map { it.roomId }
                             ?.toSet()
-                            ?: emptySet()
+                            .orEmpty()
 
                     setState {
                         copy(joinedRoomsIds = joinedRoomIds)

vector/src/main/java/im/vector/app/features/userdirectory/UserListViewModel.kt

@@ -119,7 +119,7 @@ class UserListViewModel @AssistedInject constructor(@Assisted initialState: User
                         Single.just(emptyList<User>())
                     } else {
                         val searchObservable = session.rx()
-                                .searchUsersDirectory(search, 50, state.excludedUserIds ?: emptySet())
+                                .searchUsersDirectory(search, 50, state.excludedUserIds.orEmpty())
                                 .map { users ->
                                     users.sortedBy { it.toMatrixItem().firstLetterOfDisplayName() }
                                 }