MenuScroller: fixed error when scrolling with the mouse wheel but there is nothing to scroll

Author: Federico Fissore

app/src/processing/app/tools/MenuScroller.java

@@ -441,6 +441,10 @@ private void refreshMenu() {
       firstIndex = Math.max(topFixedCount, firstIndex);
       firstIndex = Math.min(menuItems.length - bottomFixedCount - scrollCount, firstIndex);
 
+      if (firstIndex < 0) {
+        return;
+      }
+
       upItem.setEnabled(firstIndex > topFixedCount);
       downItem.setEnabled(firstIndex + scrollCount < menuItems.length - bottomFixedCount);