Merge remote-tracking branch 'origin/jetty-9.3.x' into jetty-9.4.x

jetty-security/src/main/java/org/eclipse/jetty/security/PropertyUserStore.java

@@ -128,6 +128,12 @@ public class PropertyUserStore extends AbstractLifeCycle implements PathWatcher.
      */
     public void setConfigPath(File configFile)
     {
+        if(configFile == null)
+        {
+            _configPath = null;
+            return;
+        }
+        
         _configPath = configFile.toPath();
     }