fix empty mt proof

Author: ed255

src/backends/plonky2/circuits/signedpod.rs

@@ -174,11 +174,10 @@ impl SignedPodVerifyTarget {
         assert!(curr <= self.params.max_signed_pod_values);
 
         // add the proofs of empty leaves (if needed), till the max_signed_pod_values
+        let mut mp = MerkleClaimAndProof::empty(self.params.max_depth_mt_gadget);
+        mp.root = pod.dict.commitment();
         for i in curr..self.params.max_signed_pod_values {
-            self.mt_proofs[i].set_targets(
-                pw,
-                &MerkleClaimAndProof::empty(self.params.max_depth_mt_gadget),
-            )?;
+            self.mt_proofs[i].set_targets(pw, &mp)?;
         }
 
         // get the signer pk

src/backends/plonky2/primitives/merkletree.rs

@@ -280,10 +280,10 @@ impl MerkleClaimAndProof {
         Self {
             enabled: false,
             root: EMPTY_HASH,
-            key: RawValue::from(1),
+            key: EMPTY_VALUE,
             value: EMPTY_VALUE,
             proof: MerkleProof {
-                existence: false,
+                existence: true,
                 siblings: iter::repeat(EMPTY_HASH).take(max_depth).collect(),
                 other_leaf: None,
             },