coverity#705960 Dereference before null check

Change-Id: I39253ca1e50c57564b594401f69cef4b661dbd2a

sw/source/core/uibase/uno/SwXDocumentSettings.cxx

@@ -822,8 +822,10 @@ void SwXDocumentSettings::_preGetValues ()
         throw(beans::UnknownPropertyException, beans::PropertyVetoException, lang::IllegalArgumentException, lang::WrappedTargetException )
 {
     mpDocSh = mpModel->GetDocShell();
+    if (NULL == mpDocSh)
+        throw UnknownPropertyException();
     mpDoc = mpDocSh->GetDoc();
-    if( NULL == mpDoc || NULL == mpDocSh )
+    if (NULL == mpDoc)
         throw UnknownPropertyException();
 }