Fix panic in create_transaction when payload is not exactly 32 bytes

- Add length check before copy_from_slice to prevent panic
- Generate random commitment if payload length is invalid
- Fixes issue where empty commitment string caused crash

src/silentpayments.rs

@@ -198,7 +198,12 @@ pub fn create_transaction(
 ) -> Result<SilentPaymentUnsignedTransaction> {
     let mut commitment = [0u8; 32];
     if let Some(ref p) = payload {
-        commitment.copy_from_slice(&p);
+        if p.len() == 32 {
+            commitment.copy_from_slice(&p);
+        } else {
+            // If payload is not exactly 32 bytes, generate random commitment
+            thread_rng().fill(&mut commitment);
+        }
     } else {
         thread_rng().fill(&mut commitment);
     }