[JENKINS-32765] As I am not *adding* a new import, I will annotate with @CheckForNull

Of course the import being used is in a package name that is reserved for artifacts produced by a JSR... and the JSR that the dependency is claiming to come from has not actually published anything... thus whoever produced the artifact has broken the JSR policy... and it is also not safe for us to actually use these annotations as we do not know what a JSR may change on the road to actually providing this... but that is a war for a different PR

core/src/main/java/hudson/PluginManager.java

@@ -153,6 +153,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
      * If non-null, the base directory for all exploded .hpi/.jpi plugins. Controlled by the system property / servlet
      * context parameter {@literal hudson.PluginManager.workDir}.
      */
+    @CheckForNull
     private final File workDir;
 
     /**
@@ -233,6 +234,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
      * If non-null, the base directory for all exploded .hpi/.jpi plugins.
      * @return the base directory for all exploded .hpi/.jpi plugins or {@code null} to leave this up to the strategy.
      */
+    @CheckForNull
     public File getWorkDir() {
         return workDir;
     }