fixups for player planet model updates

Stars Assistant/Services/PlanetManager.cs

@@ -85,7 +85,7 @@ public class PlanetManager : IDisposable, IEnableLogger
                     if (playerPlanet.HasValue)
                         playerPlanet.Value.Planet = planet;
                     else
-                        innerCache.Add(new PlayerPlanetViewModel(planet));
+                        innerCache.AddOrUpdate(new PlayerPlanetViewModel(planet));
                 }
             }
         );