genabi: bugfix. handle case where log has no topics

abi/abi.go

@@ -15,6 +15,7 @@ import (
 )
 
 var (
+	NoTopics      = errors.New("no data in topics")
 	SigMismatch   = errors.New("event signature doesn't match topics[0]")
 	IndexMismatch = errors.New("num indexed inputs doesn't match len(topics)")
 )

genabi/template.txt

@@ -107,6 +107,9 @@ import (
 	// event inputs from the log's data field into [{{ camel .Name }}]:
 	//	{{ .SchemaSignature }}
 	func Match{{ camel .Name }}(l abi.Log) ({{ camel .Name}}, error) {
+		if len(l.Topics) == 0 {
+			return {{ camel .Name }}{}, abi.NoTopics
+		}
 		if len(l.Topics) > 0 && {{ lower .Name }}Signature != l.Topics[0] {
 			return {{ camel .Name }}{}, abi.SigMismatch
 		}