Allow a common op. on a disposed toolbox.

Change-Id: I4da1f4daaf94456bc951b1d7a96cb28cb7fba0e9
diff --git a/vcl/source/window/toolbox2.cxx b/vcl/source/window/toolbox2.cxx
index 3b1ad8f..8394aae 100644
--- a/vcl/source/window/toolbox2.cxx
+++ b/vcl/source/window/toolbox2.cxx
@@ -937,6 +937,9 @@ sal_uInt16 ToolBox::GetItemId( const Point& rPos ) const

sal_uInt16 ToolBox::GetItemId(const OUString &rCommand) const
{
    if (!mpData)
        return TOOLBOX_ITEM_NOTFOUND;

    for (std::vector<ImplToolItem>::const_iterator it = mpData->m_aItems.begin(); it != mpData->m_aItems.end(); ++it)
    {
        if (it->maCommandStr == rCommand)