ubsan fix after "drop GetId() from SfxUndoAction"

bug introduced by
commit 64ea8306
drop GetId() from SfxUndoAction

Change-Id: I75b23650c7dc15fc76fe1b9118129ff8ead35315
Reviewed-on: https://gerrit.libreoffice.org/35333Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

sw/source/core/undo/docundo.cxx

@@ -385,7 +385,12 @@ UndoManager::GetLastUndoInfo(
     }
     if (o_pId)
     {
-        *o_pId = static_cast<const SwUndo*>(pAction)->GetId();
+        if (auto pListAction = dynamic_cast<const SfxListUndoAction*>(pAction))
+            *o_pId = (SwUndoId)pListAction->GetId();
+        else if (auto pSwAction = dynamic_cast<const SwUndo*>(pAction))
+            *o_pId = pSwAction->GetId();
+        else
+            *o_pId = SwUndoId::EMPTY;
     }
 
     return true;
@@ -443,7 +448,12 @@ bool UndoManager::GetFirstRedoInfo(OUString *const o_pStr,
     }
     if (o_pId)
     {
-        *o_pId = static_cast<const SwUndo*>(pAction)->GetId();
+        if (auto pListAction = dynamic_cast<const SfxListUndoAction*>(pAction))
+            *o_pId = (SwUndoId)pListAction->GetId();
+        else if (auto pSwAction = dynamic_cast<const SwUndo*>(pAction))
+            *o_pId = pSwAction->GetId();
+        else
+            *o_pId = SwUndoId::EMPTY;
     }
 
     return true;