Cleanup warnings for missing getPlugin() null checks (#5222)

core/src/main/java/hudson/PluginWrapper.java

@@ -523,12 +523,25 @@ public class PluginWrapper implements Comparable<PluginWrapper>, ModelObject {
 
     /**
      * Gets the instance of {@link Plugin} contributed by this plugin.
+     * @return Plugin instace or {@code null} if it is not present in the plugin instance store.
      */
     public @CheckForNull Plugin getPlugin() {
         PluginInstanceStore pis = Jenkins.lookup(PluginInstanceStore.class);
         return pis != null ? pis.store.get(this) : null;
     }
 
+    /**
+     * Gets the instance of {@link Plugin} contributed by this plugin.
+     * @throws Exception no plugin in the {@link PluginInstanceStore}
+     */
+    public @NonNull Plugin getPluginOrFail() throws Exception {
+        Plugin plugin = getPlugin();
+        if (plugin == null) {
+            throw new Exception("Cannot find the plugin instance: " + shortName);
+        }
+        return plugin;
+    }
+
     /**
      * Gets the URL that shows more information about this plugin.
      * @return