Issue Description

Migration fails on startup on first start after migration to v1.12.0

Get this error

0|reaction | TypeError: Cannot convert undefined or null to object
0|reaction |     at Function.keys (<anonymous>)
0|reaction |     at items.forEach (imports/plugins/core/versions/server/migrations/25_update_catalog_schema.js:28:12)

Steps to Reproduce

1. Start Reaction with a previous version and load data
2. Upgrade to v1.12.0
3. Observe error on startup. Migrations become locked

Versions

Node: 8.9.4
NPM: 5.6.0
Meteor Node: 8.11.2
Meteor NPM: 5.10.0
Reaction CLI: 0.29.0