swref: Use SvRef::get() instead of &*

Using &* can be problematic if the pointer is null. In this case it
doesn’t matter, but using SvRef::get() is probably easier to understand
anyway. This also paves the way for a later compiler plugin to check for
this.

Change-Id: I802417762ed323128a07d4f8ccbcf8bb8553a8c0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/211845
Reviewed-by: Neil Roberts <nroberts@libreoffice.org>
Tested-by: Jenkins

sw/source/core/doc/swserv.cxx

@@ -224,7 +224,7 @@ bool SwServerObject::IsLinkInServer( const SwBaseLink* pChkLnk ) const
             const_cast<SwServerObject*>(this)->m_eType = NONE_SERVER;
         for( size_t n = rLnks.size(); n; )
         {
-            const ::sfx2::SvBaseLink* pLnk = &(*rLnks[ --n ]);
+            const ::sfx2::SvBaseLink* pLnk = rLnks[ --n ].get();
             if (sfx2::SvBaseLinkObjectType::ClientGraphic != pLnk->GetObjType() &&
                 dynamic_cast<const SwBaseLink*>( pLnk) !=  nullptr &&
                 !static_cast<const SwBaseLink*>(pLnk)->IsNoDataFlag() &&