8049418: [macosx] PopupMenuListener.popupMenuWillBecomeVisible is not called...

8049418: [macosx] PopupMenuListener.popupMenuWillBecomeVisible is not called for empty combobox on MacOS/aqua look and feel
Reviewed-by: anthony, pchelko

src/macosx/classes/com/apple/laf/AquaComboBoxPopup.java

@@ -120,10 +120,6 @@ class AquaComboBoxPopup extends BasicComboPopup {
     public void show() {
         final int startItemCount = comboBox.getItemCount();
 
-        if (startItemCount == 0) {
-            return;
-        }
-
         final Rectangle popupBounds = adjustPopupAndGetBounds();
         if (popupBounds == null) return; // null means don't show