error when initialization of migration failes before any action.

```
[ERROR] An error occured. No alternative failure strategy defined. Rolling back! TypeError: Cannot set property 'productad' of undefined
    at Object.dropTable (/node_modules/db-migrate/lib/learn.js:32:20)
    at Chain.exec (/node_modules/db-migrate/lib/chain.js:132:38)
```
