Fix findOnce() panic

soup.go

@@ -481,6 +481,9 @@ func matchElementName(n *html.Node, name string) bool {
 
 // Using depth first search to find the first occurrence and return
 func findOnce(n *html.Node, args []string, uni bool, strict bool) (*html.Node, bool) {
+	if n == nil {
+		return nil, false
+	}
 	if uni == true {
 		if n.Type == html.ElementNode && matchElementName(n, args[0]) {
 			if len(args) > 1 && len(args) < 4 {
@@ -510,6 +513,9 @@ func findOnce(n *html.Node, args []string, uni bool, strict bool) (*html.Node, b
 
 // Using depth first search to find all occurrences and return
 func findAllofem(n *html.Node, args []string, strict bool) []*html.Node {
+	if n == nil {
+		return nil
+	}
 	var nodeLinks = make([]*html.Node, 0, 10)
 	var f func(*html.Node, []string, bool)
 	f = func(n *html.Node, args []string, uni bool) {

soup_test.go

@@ -2,6 +2,7 @@ package soup
 
 import (
 	"bytes"
+	"fmt"
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
@@ -91,6 +92,13 @@ func TestFind(t *testing.T) {
 	assert.Equal(t, "Last one", actual)
 }
 
+func TestFindOnceReturnsNil(t *testing.T) {
+	// FindOnce()
+	tag := "some tag"
+	actual := doc.Find(tag)
+	assert.Equal(t, fmt.Sprintf("element `%s` with attributes `%s` not found", tag, ""), actual.Error.Error())
+}
+
 func TestFindNextPrevElement(t *testing.T) {
 	// FindNextSibling() and NodeValue field
 	actual := doc.Find("div", "id", "0").FindNextSibling().NodeValue
@@ -290,5 +298,4 @@ func TestClient_PostForm(t *testing.T) {
 func TestHTML(t *testing.T) {
 	li := doc.Find("ul").Find("li")
 	assert.Equal(t, "<li>To a <a href=\"hello.jsp\">JSP page</a> right?</li>", li.HTML())
-
 }