SfxObjectShell may not have a medium

vbahelper/inc/vbahelper/vbaaccesshelper.hxx

@@ -63,7 +63,8 @@ namespace ooo
         VBAHELPER_DLLPRIVATE inline bool isAlienDoc( SfxObjectShell& rDocShell, const char* pMimeType )
         {
             bool bRes( false );
-            const SfxFilter *pFilt = rDocShell.GetMedium()->GetFilter();
+            const SfxMedium *pMedium = rDocShell.GetMedium();
+            const SfxFilter *pFilt = pMedium ? pMedium->GetFilter() : NULL;
             if ( pFilt && pFilt->IsAlienFormat() )
                 bRes = ( pFilt->GetMimeType().compareToAscii( pMimeType ) == 0 );
             return bRes;