Adapt to TabShell changes

Author: pcastornii

weaverbird-gui/src/main/java/com/techsenger/weaverbird/gui/WeaverbirdApplication.java

@@ -80,6 +80,7 @@ public void start(Stage stage) throws Exception {
         fileRegistrar.register();
 
         shellView.upgradeMenuBar();
+        stage.show();
     }
 
 }