Fix error: title is required.

Related https://github.com/wekan/wekan/commit/8d5cbf1e6c2b6d467fe1c0708cd794fd11b98a2e

Closes #1576

server/migrations.js

@@ -193,7 +193,7 @@ Migrations.add('add-checklist-items', () => {
     // Create new items
     _.sortBy(checklist.items, 'sort').forEach((item, index) => {
       ChecklistItems.direct.insert({
-        title: item.title,
+        title: checklist.title,
         sort: index,
         isFinished: item.isFinished,
         checklistId: checklist._id,