feat(jqLite): don't throw for elements with missing getAttribute

jQuery falls back to prop here but this feature is not very well tested
& documented so let's just skip it here.

Closes #15181

src/jqLite.js

@@ -640,7 +640,8 @@ forEach({
   attr: function(element, name, value) {
     var ret;
     var nodeType = element.nodeType;
-    if (nodeType === NODE_TYPE_TEXT || nodeType === NODE_TYPE_ATTRIBUTE || nodeType === NODE_TYPE_COMMENT) {
+    if (nodeType === NODE_TYPE_TEXT || nodeType === NODE_TYPE_ATTRIBUTE || nodeType === NODE_TYPE_COMMENT ||
+      !element.getAttribute) {
       return;
     }
 
@@ -655,7 +656,7 @@ forEach({
       } else {
         element.setAttribute(name, isBooleanAttr ? lowercasedName : value);
       }
-    } else if (element.getAttribute) {
+    } else {
       // getter
 
       ret = element.getAttribute(name);

test/jqLiteSpec.js

@@ -751,6 +751,17 @@ describe('jqLite', function() {
       elm.attr('multiple', '');
       expect(elm[0].getAttribute('multiple')).toBe('multiple');
     });
+
+    it('should not fail on elements without the getAttribute method', function() {
+      forEach([window, document], function(node) {
+        expect(function() {
+          var elem = jqLite(node);
+          elem.attr('foo');
+          elem.attr('bar', 'baz');
+          elem.attr('bar');
+        }).not.toThrow();
+      });
+    });
   });