dont update iframe src attribute if it is empty

STUD-1136

cms/static/js/spec/utils/handle_iframe_binding_spec.js

 define(
     [
         "jquery", "underscore",
-        "js/utils/handle_iframe_binding",
+        "js/utils/handle_iframe_binding"
     ],
 function ($, _, IframeBinding) {
 
@@ -33,5 +33,14 @@ function ($, _, IframeBinding) {
                 '<iframe src="http://www.youtube.com/embed/NHd27UvY-lw?wmode=transparent&amp;allowFullScreen=false" frameborder="0" height="350" width="618"></iframe>' +
                 '<embed wmode="transparent" type="application/x-shockwave-flash" src="http://www.youtube.com/embed/NHd27UvY-lw" height="315" width="560">');
         });
+
+        it("does not modify src url of DOM iframe if it is empty", function () {
+            iframe_html = '<iframe width="618" height="350" src="" frameborder="0" allowfullscreen></iframe>';
+            doc.body.innerHTML = iframe_html;
+
+            IframeBinding.iframeBinding(doc);
+
+            expect($(doc).find("iframe")[0].src).toEqual("");
+        });
     });
 });

cms/static/js/utils/handle_iframe_binding.js

 define(["jquery"], function($) {
     var iframeBinding = function (e) {
         var target_element = null;
-        if (typeof(e) == "undefined"){
+        if (typeof(e) === "undefined") {
             target_element = $("iframe, embed");
         } else {
-            if (typeof(e.nodeName) != 'undefined'){
+            if (typeof(e.nodeName) !== 'undefined') {
                 target_element = $(e).find("iframe, embed");
-            } else{
+            } else {
                 target_element = e.$("iframe, embed");
             }
         }
@@ -14,21 +14,27 @@ define(["jquery"], function($) {
     };
 
     var modifyTagContent = function (target_element) {
-        target_element.each(function(){
-            if ($(this).prop('tagName') == 'IFRAME'){
+        target_element.each(function() {
+            if ($(this).prop('tagName') === 'IFRAME') {
                 var ifr_source = $(this).attr('src');
-                var wmode = "wmode=transparent";
-                if(ifr_source.indexOf('?') != -1) {
-                    var getQString = ifr_source.split('?');
-                    if (getQString[1].search('wmode=transparent') == -1){
-                        var oldString = getQString[1];
-                        var newString = getQString[0];
-                        $(this).attr('src',newString+'?'+wmode+'&'+oldString);
+
+                // Modify iframe src only if it is not empty
+                if (ifr_source) {
+                    var wmode = "wmode=transparent";
+                    if (ifr_source.indexOf('?') !== -1) {
+                        var getQString = ifr_source.split('?');
+                        if (getQString[1].search('wmode=transparent') === -1) {
+                            var oldString = getQString[1];
+                            var newString = getQString[0];
+                            $(this).attr('src', newString + '?' + wmode + '&' + oldString);
+                        }
+                    }
+                    else {
+                        $(this).attr('src', ifr_source + '?' + wmode);
                     }
                 }
-                else $(this).attr('src',ifr_source+'?'+wmode);
             }
-            else{
+            else {
                 $(this).attr('wmode', 'transparent');
             }
         });