Resolve fdo#79913 by checking index bounds

Change-Id: I023a625d73724332245d612a61cb786acefc4cf2
Reviewed-on: https://gerrit.libreoffice.org/9791Reviewed-by: Jean-Baptiste Faure <jbfaure@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

svtools/source/control/toolbarmenu.cxx

@@ -397,7 +397,7 @@ void ToolbarMenu_Impl::notifyHighlightedEntry()
                 if( pValueSet )
                     nChildIndex = static_cast< sal_Int32 >( pValueSet->GetItemPos( pValueSet->GetSelectItemId() ) );
 
-                if( nChildIndex >= pEntry->getAccessibleChildCount() )
+                if( (nChildIndex >= pEntry->getAccessibleChildCount()) || (nChildIndex < 0) )
                     return;
 
                 aNew <<= getAccessibleChild( pEntry->mpControl, nChildIndex );