These fixes aren't needed after all.

The root problem was instead fixed by...

commit 144e73f5
Author: Noel Grandin <noel@peralex.com>
Date:   Tue Dec 22 09:05:32 2015 +0200

    fix Link::operator<

    so that it is consistent with operator==

Revert "Related: rhbz#1343766 a11y queries during dispose trigger listbox crashes"

This reverts commit c615943b.

Revert "Resolves: rhbz#1343766 a11y queries during dispose trigger combobox crashes"

This reverts commit f120abb4.

vcl/source/control/combobox.cxx

@@ -1000,15 +1000,11 @@ OUString ComboBox::GetEntry( sal_Int32 nPos ) const
 
 sal_Int32 ComboBox::GetEntryCount() const
 {
-    if (!m_pImpl->m_pImplLB)
-        return 0;
     return m_pImpl->m_pImplLB->GetEntryList()->GetEntryCount() - m_pImpl->m_pImplLB->GetEntryList()->GetMRUCount();
 }
 
 bool ComboBox::IsTravelSelect() const
 {
-    if (!m_pImpl->m_pImplLB)
-        return false;
     return m_pImpl->m_pImplLB->IsTravelSelect();
 }
 
@@ -1025,8 +1021,6 @@ void ComboBox::EnableMultiSelection( bool bMulti )
 
 bool ComboBox::IsMultiSelectionEnabled() const
 {
-    if (!m_pImpl->m_pImplLB)
-        return false;
     return m_pImpl->m_pImplLB->IsMultiSelectionEnabled();
 }
 

vcl/source/control/listbox.cxx

@@ -1190,8 +1190,6 @@ void ListBox::EnableMultiSelection( bool bMulti, bool bStackSelection )
 
 bool ListBox::IsMultiSelectionEnabled() const
 {
-    if (!mpImplLB)
-        return false;
     return mpImplLB->IsMultiSelectionEnabled();
 }