Correct measurement for owner drawn menu items with only unchecked bitmap.

Check for either checked or unchecked bitmap being specified for the item
instead of checking the checked/normal bitmap twice which was an obvious typo
and also resulted in items with unchecked bitmap only not being measured
correctly (although I'm not sure if this is actually a supported use case).

Closes #12846.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66602 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/menuitem.cpp

@@ -882,7 +882,7 @@ bool wxMenuItem::OnMeasureItem(size_t *width, size_t *height)
         *width += imgWidth + data->CheckBgMargin.GetTotalX();
     }
 
-    if ( m_bmpChecked.IsOk() || m_bmpChecked.IsOk() )
+    if ( m_bmpChecked.IsOk() || m_bmpUnchecked.IsOk() )
     {
         // get size of bitmap always return valid value (0 for invalid bitmap),
         // so we don't needed check if bitmap is valid ;)