Added placeholder image to HelpMenu if links unavailable (#2899)

Author: jinapurapu

portal-ui/src/placeholderimage.png

@@ -17,6 +17,7 @@
 import React, { Fragment } from "react";
 import { DocItem } from "./HelpMenu.types";
 import MoreLink from "../../common/MoreLink";
+import placeholderImg from "../../placeholderimage.png";
 
 interface IHelpItemProps {
   item: DocItem;
@@ -50,7 +51,7 @@ const HelpItem = ({ item, displayImage = true }: IHelpItemProps) => {
                   style={{
                     width: 208,
                     height: 116,
-                    backgroundImage: `url(${item.img})`,
+                    backgroundImage: `url(${item.img}), url(${placeholderImg})`,
                     backgroundPosition: "center center",
                     backgroundSize: "cover",
                     backgroundRepeat: "no-repeat",