Fix the room list flashing empty on launch

The room summary provider publishes its loading state and its rooms through two
independent streams, so the state can report loaded before the first summaries
have been applied. Flipping the room list mode to .rooms at that point renders
an empty list until the summaries arrive.

Combine the two publishers into a single subscription so that the mode and the
rooms are always updated from the same pair of values, and keep the skeletons up
until the rooms have published. Only the initial transition is held back, an
empty list later on is a filter or a search result and must not send the mode
back to the skeletons.

ElementX/Sources/Screens/HomeScreen/HomeScreenViewModel.swift

@@ -313,33 +313,34 @@ class HomeScreenViewModel: HomeScreenViewModelType, HomeScreenViewModelProtocol
             return
         }
         
+        // Combined so that the mode and the rooms are always updated from the same pair of
+        // values: the state can report loaded before the first summaries have published and
+        // flipping to .rooms then would flash an empty list.
         roomSummaryProvider.statePublisher
+            .combineLatest(roomSummaryProvider.roomListPublisher)
             .receive(on: DispatchQueue.main)
-            .sink { [weak self] state in
+            .sink { [weak self] state, rooms in
                 guard let self else { return }
                 
-                updateRoomListMode(with: state)
-            }
-            .store(in: &cancellables)
-        
-        roomSummaryProvider.roomListPublisher
-            .receive(on: DispatchQueue.main)
-            .sink { [weak self] _ in
-                self?.updateRooms()
+                updateRooms()
+                updateRoomListMode(with: state, hasRooms: !rooms.isEmpty)
             }
             .store(in: &cancellables)
     }
     
-    private func updateRoomListMode(with roomSummaryProviderState: RoomSummaryProviderState) {
+    private func updateRoomListMode(with roomSummaryProviderState: RoomSummaryProviderState, hasRooms: Bool) {
         let isLoadingData = !roomSummaryProviderState.isLoaded
         let hasNoRooms = roomSummaryProviderState.isLoaded && roomSummaryProviderState.totalNumberOfRooms == 0
+        // Only the initial transition needs holding back until the rooms have published, an
+        // empty list later on is a filter or a search result.
+        let isInitialLoad = state.roomListMode == .skeletons
         
         var roomListMode = state.roomListMode
         if isLoadingData {
             roomListMode = .skeletons
         } else if hasNoRooms {
             roomListMode = .empty
-        } else {
+        } else if hasRooms || !isInitialLoad {
             roomListMode = .rooms
         }