Handle native querySelector returning nothing

	- Fixes #476
	- Added tests

src/querySelector.js

@@ -128,7 +128,11 @@
         return findOne(this, selector);
       }
 
-      if (root = getTreeScope(wrappedItem).root) {
+      if (!wrappedItem) {
+        // When the original query returns nothing
+        // we return nothing (to be consistent with the other wrapped calls)
+        return wrappedItem;
+      } else if (root = getTreeScope(wrappedItem).root) {
         if (root instanceof scope.wrappers.ShadowRoot) {
           // When the original query returns an element in the ShadowDOM
           // we must do a manual tree traversal

test/js/Document.js

@@ -87,6 +87,9 @@ htmlSuite('Document', function() {
     assert.equal(elements.length, 2);
     assert.equal(elements[0], aa3);
     assert.equal(elements[1], aa4);
+
+    var z = document.getElementsByTagName('z');
+    assert.equal(z.length, 0);
   });
 
   test('getElementsByTagNameNS', function() {
@@ -176,6 +179,14 @@ htmlSuite('Document', function() {
     assert.equal(elements.length, 2);
     assert.equal(elements[0], aa3);
     assert.equal(elements[1], aa4);
+
+    var z = document.querySelectorAll('z');
+    assert.equal(z.length, 0);
+  });
+
+  skipTest('querySelector', function() {
+    var z = document.querySelector('z');
+    assert.equal(z, null);
   });
 
   test('addEventListener', function() {

test/js/Element.js

@@ -31,6 +31,12 @@ suite('Element', function() {
 
     assert.equal(div.querySelector('b'), b);
     assert.equal(sr.querySelector('b'), srb);
+
+    var z = div.querySelector('z');
+    assert.equal(z, null);
+
+    var z = sr.querySelector('z');
+    assert.equal(z, null);
   });
 
   skipTest('querySelectorAll', function() {
@@ -62,6 +68,12 @@ suite('Element', function() {
     assert.equal(as.length, 2);
     assert.equal(as[0], a3);
     assert.equal(as[1], a4);
+
+    var z = div.querySelectorAll('z');
+    assert.equal(z.length, 0);
+
+    var z = sr.querySelectorAll('z');
+    assert.equal(z.length, 0);
   });
 
   skipTest('getElementsByTagName', function() {
@@ -93,6 +105,12 @@ suite('Element', function() {
     assert.equal(as.length, 2);
     assert.equal(as[0], a3);
     assert.equal(as[1], a4);
+
+    var z = div.getElementsByTagName('z');
+    assert.equal(z.length, 0);
+
+    var z = sr.getElementsByTagName('z');
+    assert.equal(z.length, 0);
   });
 
   test('getElementsByTagName with colon', function() {
@@ -138,6 +156,20 @@ suite('Element', function() {
     assert.equal(as.item(2), a3);
   });
 
+  test('getElementsByTagNameNS', function() {
+    var div = document.createElement('div');
+    div.innerHTML = '<a>0</a><a>1</a>';
+
+    var sr = div.createShadowRoot();
+    sr.innerHTML = '<a>3</a><a>4</a>';
+
+    var z = div.getElementsByTagNameNS('NS', 'z');
+    assert.equal(z.length, 0);
+
+    var z = sr.getElementsByTagNameNS('NS', 'z');
+    assert.equal(z.length, 0);
+  });
+
   skipTest('getElementsByClassName', function() {
     var div = document.createElement('div');
     div.innerHTML = '<span class=a>0</span><span class=a>1</span>';