Account for fuzz HTLC signature weight

When secp256k1_fuzz is active, dummy ECDSA signatures may
serialize one byte larger per signature. Add two WU to the
HTLC-resolution witness estimates so debug weight assertions use the
fuzz signer bound.

Author: joostjager

lightning/src/events/bump_transaction/mod.rs

@@ -547,6 +547,11 @@ impl<B: BroadcasterInterface, C: CoinSelectionSource, SP: SignerProvider, L: Log
 			} else {
 				panic!("channel type should be either zero-fee HTLCs, or zero-fee commitments");
 			};
+		// The secp256k1 fuzz signer emits dummy signatures without low-S normalization, so
+		// DER+sighash can be one byte larger for each of the two HTLC signatures.
+		#[cfg(secp256k1_fuzz)]
+		let (htlc_success_witness_weight, htlc_timeout_witness_weight) =
+			(htlc_success_witness_weight + 2, htlc_timeout_witness_weight + 2);
 
 		let max_tx_weight = if channel_type.supports_anchor_zero_fee_commitments() {
 			// Cap the size of transactions claiming `HolderHTLCOutput` in 0FC channels.