tdf#115090 keep internal BaseModel alive long enough

There's reams of code already preventing a close during save
(SfxSaveGuard), but this looks equally effective. Avoids
SfxBaseModel::dispose() pulling the rug under us, when
SfxBaseModel::postEvent_Impl() wants to access parts of the
interface containers during notification.

Change-Id: Iace1f9922c47a97ab2e798b577c6aec8a729da48
Reviewed-on: https://gerrit.libreoffice.org/48709Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

include/sfx2/sfxbasemodel.hxx

@@ -739,7 +739,7 @@ private:
 
 private:
 
-    std::unique_ptr<IMPL_SfxBaseModel_DataContainer> m_pData;
+    std::shared_ptr<IMPL_SfxBaseModel_DataContainer> m_pData;
     // cannot be held in m_pData, since it needs to be accessed in non-threadsafe context
     const bool                          m_bSupportEmbeddedScripts;
     const bool                          m_bSupportDocRecovery;

sfx2/source/doc/sfxbasemodel.cxx

@@ -3062,6 +3062,9 @@ void SfxBaseModel::postEvent_Impl( const OUString& aName, const Reference< frame
     if ( impl_isDisposed() )
         return;
 
+    // keep m_pData alive, if notified target would close the document
+    std::shared_ptr<IMPL_SfxBaseModel_DataContainer> pData(m_pData);
+
     DBG_ASSERT( !aName.isEmpty(), "Empty event name!" );
     if (aName.isEmpty())
         return;