fdo#84617: Guard the destructor with SolarMutex.

The same pattern as introduced elsewhere recently.

Change-Id: Ie7b4fd1ec26d417f63bee26dd336dfc54f4847dc

sd/source/ui/app/sdxfer.cxx

@@ -110,6 +110,8 @@ SdTransferable::SdTransferable( SdDrawDocument* pSrcDoc, ::sd::View* pWorkView,
 
 SdTransferable::~SdTransferable()
 {
+    SolarMutexGuard g;
+
     if( mpSourceDoc )
         EndListening( *mpSourceDoc );