frontend: Hide back button with null backLink

This fix explicitly handles the null case in getBackLink() to ensure
that no back button will be shown, as defined in MainInfoSectionProps.

Fixes: #2033

Signed-off-by: Evangelos Skopelitis <eskopelitis@microsoft.com>

frontend/src/components/common/Resource/MainInfoSection/MainInfoSection.tsx

@@ -49,6 +49,10 @@ export function MainInfoSection(props: MainInfoSectionProps) {
   const header = typeof headerSection === 'function' ? headerSection(resource) : headerSection;
 
   function getBackLink() {
+    if (backLink === null) {
+      return false;
+    }
+
     if (!!backLink || backLink === '') {
       return backLink;
     }