Temporarily populate new subtree fields with None - for revert

This temporary commit needs to be reverted in the next PR.

zebra-state/src/request.rs

@@ -241,7 +241,9 @@ impl Treestate {
             note_commitment_trees: NoteCommitmentTrees {
                 sprout,
                 sapling,
+                sapling_subtree: None,
                 orchard,
+                orchard_subtree: None,
             },
             history_tree,
         }

zebra-state/src/service/finalized_state/zebra_db/shielded.rs

@@ -224,7 +224,9 @@ impl ZebraDb {
         NoteCommitmentTrees {
             sprout: self.sprout_tree(),
             sapling: self.sapling_tree(),
+            sapling_subtree: None,
             orchard: self.orchard_tree(),
+            orchard_subtree: None,
         }
     }
 }

zebra-state/src/service/non_finalized_state/chain.rs

@@ -1251,7 +1251,9 @@ impl Chain {
         let mut nct = NoteCommitmentTrees {
             sprout: self.sprout_note_commitment_tree(),
             sapling: self.sapling_note_commitment_tree(),
+            sapling_subtree: None,
             orchard: self.orchard_note_commitment_tree(),
+            orchard_subtree: None,
         };
 
         let mut tree_result = None;