Match empty string if start state is kleene star

matching.go

@@ -31,6 +31,10 @@ func findAllMatches(start *State, str string) (indices []matchIndex) {
 func findAllMatchesHelper(start *State, str string, indices []matchIndex, offset int) []matchIndex {
 	// 'Base case' - exit if string is empty.
 	if len(str) == 0 {
+		// If the start is a Kleene star, then it should also match an empty string.
+		if start.isKleene {
+			indices = append(indices, matchIndex{offset, offset})
+		}
 		return indices
 	}