Fix duplicate Folders bug

csharp/App/Backend/Database/Db.cs

@@ -89,19 +89,23 @@ public partial class Db : IDisposable
     
     public IEnumerable<Installation> GetAllAccessibleInstallations(User user)
     {
-        var direct      = GetDirectlyAccessibleInstallations(user).ToList();
+        var direct      = GetDirectlyAccessibleInstallations(user);
         var fromFolders = GetAllAccessibleFolders(user)
-                         .SelectMany(GetChildInstallations)
+                         .SelectMany(GetChildInstallations);
-                         .Except(direct);
 
-        return direct.Concat(fromFolders);
+        return direct
+              .Concat(fromFolders)
+              .Distinct();
     }
-    
   
     public IEnumerable<Folder> GetAllAccessibleFolders(User user)
     {
         return GetDirectlyAccessibleFolders(user)
-              .SelectMany(GetDescendantFolders);
+              .SelectMany(GetDescendantFolders)
+              .Distinct();  
+        
+        // Distinct because the user might have direct access
+        // to a child folder of a folder he has already access to 
     }