Resolves: tdf#100275 makeMark may return null under some circumstances

Change-Id: If3b83413c028c6cd1c055e632b6f050ec7f2475d

sw/source/core/doc/DocumentContentOperationsManager.cxx

@@ -254,9 +254,12 @@ namespace
                 aTmpPam,
                 pMark->GetName(),
                 IDocumentMarkAccess::GetType(*pMark));
-            // Explicitly try to get exactly the same name as in the source
-            // because NavigatorReminders, DdeBookmarks etc. ignore the proposed name
-            pDestDoc->getIDocumentMarkAccess()->renameMark(pNewMark, pMark->GetName());
+            if (pNewMark)
+            {
+                // Explicitly try to get exactly the same name as in the source
+                // because NavigatorReminders, DdeBookmarks etc. ignore the proposed name
+                pDestDoc->getIDocumentMarkAccess()->renameMark(pNewMark, pMark->GetName());
+            }
 
             // copying additional attributes for bookmarks or fieldmarks
             ::sw::mark::IBookmark* const pNewBookmark =