gcs/builder: skip zero nil outputs scripts

gcs/builder/builder.go

@@ -331,6 +331,10 @@ func BuildBasicFilter(block *wire.MsgBlock, prevOutScripts [][]byte) (*gcs.Filte
 		// For each output in a transaction, we'll add each of the
 		// individual data pushes within the script.
 		for _, txOut := range tx.TxOut {
+			if len(txOut.PkScript) == 0 {
+				continue
+			}
+
 			// In order to allow the filters to later be committed
 			// to within an OP_RETURN output, we ignore all
 			// OP_RETURNs to avoid a circular dependency.
@@ -346,6 +350,10 @@ func BuildBasicFilter(block *wire.MsgBlock, prevOutScripts [][]byte) (*gcs.Filte
 	// In the second pass, we'll also add all the prevOutScripts
 	// individually as elements.
 	for _, prevScript := range prevOutScripts {
+		if len(prevScript) == 0 {
+			continue
+		}
+
 		b.AddEntry(prevScript)
 	}