tdf#107706 fix crash when closing Calc document

regression from commit e8b49f09074fe184374bee5062715357427ae044
"new loplugin: useuniqueptr: vcl"

Change-Id: I07ac157a02aa82b1ddbb741797fea093772f93f1
Reviewed-on: https://gerrit.libreoffice.org/37470
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>
diff --git a/svx/source/tbxctrls/tbunosearchcontrollers.cxx b/svx/source/tbxctrls/tbunosearchcontrollers.cxx
index 9439189..a3b2a06 100644
--- a/svx/source/tbxctrls/tbunosearchcontrollers.cxx
+++ b/svx/source/tbxctrls/tbunosearchcontrollers.cxx
@@ -226,6 +226,8 @@ void FindTextFieldControl::SetTextToSelected_Impl()

bool FindTextFieldControl::PreNotify( NotifyEvent& rNEvt )
{
    if (isDisposed())
        return true;
    bool bRet= ComboBox::PreNotify( rNEvt );

    switch ( rNEvt.GetType() )