fix ClassNotFound exception when running on a stock JDK without GraalJS

Author: Gubaer

src/main/java/org/openstreetmap/josm/plugins/scripting/preferences/graalvm/GraalVMConfigurationPanel.java

@@ -64,8 +64,10 @@ protected JPanel buildInfoPanel() {
     protected JPanel buildTabs() {
         JPanel pnl = new JPanel(new BorderLayout());
         JTabbedPane tpPreferencesTabs = new JTabbedPane();
-        tpPreferencesTabs.add(tr("ES Module repositories"),
-            pnlESModuleRepoConfiguration = new ESModuleRepoConfigurationPanel());
+        if (GraalVMFacadeFactory.isGraalVMPresent()) {
+            tpPreferencesTabs.add(tr("ES Module repositories"),
+                pnlESModuleRepoConfiguration = new ESModuleRepoConfigurationPanel());
+        }
         tpPreferencesTabs.add(tr("CommonJS module repositories"),
             pnlCommonJSRepoConfiguration = new CommonJSRepoConfigurationPanel());
         pnl.add(tpPreferencesTabs, BorderLayout.CENTER);