MC-30403: 'What is this ?' button does not work correctly

- Resolved static test failures

Author: Hwashiang Yu

app/code/Magento/Backend/Block/Store/Switcher.php

@@ -462,7 +462,7 @@ public function getCurrentSelectionName()
     /**
      * Get current website name
      *
-     * @return string
+     * @return string | null
      */
     public function getCurrentWebsiteName()
     {
@@ -473,12 +473,14 @@ public function getCurrentWebsiteName()
                 return $website->getName();
             }
         }
+
+        return null;
     }
 
     /**
      * Get current store group name
      *
-     * @return string
+     * @return string | null
      */
     public function getCurrentStoreGroupName()
     {
@@ -489,12 +491,14 @@ public function getCurrentStoreGroupName()
                 return $group->getName();
             }
         }
+
+        return null;
     }
 
     /**
      * Get current store view name
      *
-     * @return string
+     * @return string | null
      */
     public function getCurrentStoreName()
     {
@@ -505,6 +509,8 @@ public function getCurrentStoreName()
                 return $store->getName();
             }
         }
+
+        return null;
     }
 
     /**