make AttrOr return default value if selection is empty

property.go

@@ -23,7 +23,7 @@ func (s *Selection) Attr(attrName string) (val string, exists bool) {
 // AttrOr works like Attr but returns default value if attribute is not present.
 func (s *Selection) AttrOr(attrName, defaultValue string) string {
 	if len(s.Nodes) == 0 {
-		return ""
+		return defaultValue
 	}
 
 	val, exists := getAttributeValue(attrName, s.Nodes[0])

property_test.go

@@ -20,6 +20,11 @@ func TestAttrOr(t *testing.T) {
 	} else {
 		t.Logf("Value returned for not existing attribute: %v.", val)
 	}
+	if val := Doc().Find("zz").AttrOr("fake-attribute", "alternative"); val != "alternative" {
+		t.Error("Expected an alternative value for 'fake-attribute' on an empty selection.")
+	} else {
+		t.Logf("Value returned for empty selection: %v.", val)
+	}
 }
 
 func TestAttrNotExist(t *testing.T) {