Adds another element existence check to avoid JS errors in welcome page.

app.js

@@ -1150,13 +1150,14 @@ $(document).ready(function () {
         if (interfaceConfig.SHOW_BRAND_WATERMARK) {
             var rightWatermarkDiv
                 = $("#welcome_page_header div[class='watermark rightwatermark']");
-
+            if(rightWatermarkDiv && rightWatermarkDiv.length > 0) {
                 rightWatermarkDiv.css({display: 'block'});
                 rightWatermarkDiv.parent().get(0).href
                     = interfaceConfig.BRAND_WATERMARK_LINK;
                 rightWatermarkDiv.get(0).style.backgroundImage
                     = "url(../images/rightwatermark.png)";
             }
+        }
 
         if (interfaceConfig.SHOW_POWERED_BY) {
             $("#welcome_page_header>a[class='poweredby']")