tdf#118452 Don't crash when multi thread calculation is disabled

...by default configuration.

Change-Id: If6075ae66537f613434dd38766324436f2426517
Reviewed-on: https://gerrit.libreoffice.org/56840
Tested-by: Jenkins
Reviewed-by: Andras Timar <andras.timar@collabora.com>
(cherry picked from commit e119194a)
Reviewed-on: https://gerrit.libreoffice.org/56856

sc/source/ui/optdlg/tpcalc.cxx

@@ -183,7 +183,7 @@ void ScTpCalcOptions::Reset( const SfxItemSet* /* rCoreAttrs */ )
         m_pEdPrec->SetValue(nPrec);
     }
 
-    m_pBtnThread->Enable();
+    m_pBtnThread->Enable( !officecfg::Office::Calc::Formula::Calculation::UseThreadedCalculationForFormulaGroups::isReadOnly() );
     m_pBtnThread->Check( officecfg::Office::Calc::Formula::Calculation::UseThreadedCalculationForFormulaGroups::get() );
 
     CheckClickHdl(m_pBtnIterate);