Merge pull request #2 from wneessen/empty-subject-fix

Fix index out of range error when no subject is set

subject_capitalize/subject_capitalize.go

@@ -24,6 +24,9 @@ func New(l language.Tag) *Middleware {
 // Handle is the handler method that satisfies the mail.Middleware interface
 func (c Middleware) Handle(m *mail.Msg) *mail.Msg {
 	cs := m.GetGenHeader(mail.HeaderSubject)
+	if len(cs) <= 0 {
+		return m
+	}
 	cp := cases.Title(c.l)
 	m.Subject(cp.String(cs[0]))
 	return m

subject_capitalize/subject_capitalize_test.go

@@ -31,3 +31,11 @@ func TestMiddleware_Handle(t *testing.T) {
 		t.Errorf("middleware failed. Expected: %q in subject, got: %q", "This Is A Test", buf.String())
 	}
 }
+
+func TestMiddleware_HandleEmpty(t *testing.T) {
+	m := mail.NewMsg(mail.WithMiddleware(New(language.English)))
+	buf := bytes.Buffer{}
+	if _, err := m.WriteTo(&buf); err != nil {
+		t.Errorf("failed to write mail message to buffer: %s", err)
+	}
+}