Avoid panic when signing is cancelled

Author: dmakarov

src/bin/sys.rs

@@ -3407,7 +3407,7 @@ async fn process_account_split<T: Signers>(
         into_keypair.pubkey(),
     );
 
-    transaction.partial_sign(&signers, recent_blockhash);
+    transaction.try_partial_sign(&signers, recent_blockhash)?;
     transaction.try_sign(&[&into_keypair], recent_blockhash)?;
 
     let signature = transaction.signatures[0];