fix(cliv2): scanning fails when birthday block does not exist

When the wallet is just created, there is no blocks on the LocalChain,
making the request of the birthday checkpoint impossible to serve.

This change avoids the issue by directly using the height and hash set
on the wallet.birthday field.

Author: nymius

cli/v2/src/main.rs

@@ -335,13 +335,7 @@ async fn main() -> anyhow::Result<()> {
                 let hash = wallet.chain().tip().hash();
                 HeaderCheckpoint::new(height, hash)
             } else {
-                let checkpoint = wallet
-                    .chain()
-                    .get(wallet.birthday.height)
-                    .expect("should be something");
-                let height = checkpoint.height();
-                let hash = checkpoint.hash();
-                HeaderCheckpoint::new(height, hash)
+                HeaderCheckpoint::new(wallet.birthday.height, wallet.birthday.hash)
             };
 
             tracing::info!(