fix: use TransactionMustHaveAnInput from ringct

* remove Error::TransactionMustHaveAnInput from test cases
* check for blst_ringct::Error::TransactionMustHaveAnInput

src/dbc.rs

@@ -390,7 +390,9 @@ pub(crate) mod tests {
 
         assert!(matches!(
             dbc.confirm_valid(&owner_once.owner_base().secret_key()?, &mint_key_manager),
-            Err(Error::TransactionMustHaveAnInput)
+            Err(Error::RingCt(
+                blst_ringct::Error::TransactionMustHaveAnInput
+            ))
         ));
 
         Ok(())
@@ -634,7 +636,7 @@ pub(crate) mod tests {
                     .iter()
                     .any(|o| *o.public_key() == dbc_owner));
             }
-            Err(Error::TransactionMustHaveAnInput) => {
+            Err(Error::RingCt(blst_ringct::Error::TransactionMustHaveAnInput)) => {
                 assert_eq!(n_inputs.coerce::<u8>(), 0);
             }
             Err(Error::FailedSignature) => {

src/error.rs

@@ -42,9 +42,6 @@ pub enum Error {
     #[error("Transaction hash does not match the transaction signed by spentbook")]
     InvalidTransactionHash,
 
-    #[error("The DBC transaction must have at least one input")]
-    TransactionMustHaveAnInput,
-
     #[error("Dbc Content is not a member of transaction outputs")]
     DbcContentNotPresentInTransactionOutput,
 

src/mint.rs

@@ -470,7 +470,7 @@ mod tests {
                 Error::RingCt(blst_ringct::Error::InvalidHiddenCommitmentInRing) => {
                     assert!(!invalid_spent_proofs.is_empty());
                 }
-                Error::TransactionMustHaveAnInput => {
+                Error::RingCt(blst_ringct::Error::TransactionMustHaveAnInput) => {
                     assert_eq!(input_amounts.len(), 0);
                 }
                 Error::FailedSignature => {