tdf#107458 No active item for the overflow subtoolbar

Item id 0 has two meanings inside ToolBox. Methods like
GetCurItemId and GetDownItemId use it as "no item".
But that's also the id of a separator item, so calling
GetItemPos(0) will find a separator, if the ToolBox has
one.

Change-Id: I4f2c1fac1759fe0a3ae09d317909707084e16180
diff --git a/accessibility/source/standard/vclxaccessibletoolbox.cxx b/accessibility/source/standard/vclxaccessibletoolbox.cxx
index aa4cad6..b8dd8e2 100644
--- a/accessibility/source/standard/vclxaccessibletoolbox.cxx
+++ b/accessibility/source/standard/vclxaccessibletoolbox.cxx
@@ -421,8 +421,8 @@ void VCLXAccessibleToolBox::UpdateCustomPopupItemp_Impl( vcl::Window* pWindow, b
    {
        const sal_uInt16 nDownItem = pToolBox->GetDownItemId();
        if ( !nDownItem )
            // Items with ItemId == 0 are not allowed in ToolBox, which means that currently no item is in down state.
            // Moreover, running GetItemPos with 0 could find a separator item if there is any.
            // No item is currently in down state.
            // Moreover, calling GetItemPos with 0 will find a separator if there is any.
            return;

        Reference< XAccessible > xChild( pWindow->GetAccessible() );
@@ -461,7 +461,13 @@ void VCLXAccessibleToolBox::HandleSubToolBarEvent( const VclWindowEvent& rVclWin
        && pToolBox == pChildWindow->GetParent()
        && pChildWindow->GetType() == WindowType::TOOLBOX )
    {
        ToolBox::ImplToolItems::size_type nIndex = pToolBox->GetItemPos( pToolBox->GetCurItemId() );
        const sal_uInt16 nCurItemId( pToolBox->GetCurItemId() );
        if ( !nCurItemId )
            // No item is currently active (might happen when opening the overflow popup).
            // Moreover, calling GetItemPos with 0 will find a separator if there is any.
            return;

        ToolBox::ImplToolItems::size_type nIndex = pToolBox->GetItemPos( nCurItemId );
        Reference< XAccessible > xItem = getAccessibleChild( nIndex );
            //TODO: ToolBox::ImplToolItems::size_type -> sal_Int32!
        if ( xItem.is() )