Fixed unified inbox folders with child folders

app/src/main/java/eu/faircode/email/AdapterFolder.java

@@ -690,6 +690,10 @@ public class AdapterFolder extends RecyclerView.Adapter<AdapterFolder.ViewHolder
         if (folders.size() > 0)
             Collections.sort(folders, folders.get(0).getComparator(context));
 
+        List<TupleFolderEx> hierarchical;
+        if (account < 0)
+            hierarchical = folders;
+        else {
             List<TupleFolderEx> parents = new ArrayList<>();
             Map<Long, TupleFolderEx> idFolder = new HashMap<>();
             Map<Long, List<TupleFolderEx>> parentChilds = new HashMap<>();
@@ -720,7 +724,8 @@ public class AdapterFolder extends RecyclerView.Adapter<AdapterFolder.ViewHolder
                 }
             }
 
-        List<TupleFolderEx> hierarchical = getHierarchical(parents, 0);
+            hierarchical = getHierarchical(parents, 0);
+        }
 
         DiffUtil.DiffResult diff = DiffUtil.calculateDiff(new DiffCallback(items, hierarchical), false);