Data-migration-tool: Sales Order Grid - Array to string conversion exception when running Deltas

[DanCarlyon]

Preconditions

1. Magento 1 version is 1.14.2.3
2. Magento 2 version is 2.2.6 (Was also an issue on 2.2.5)
3. PHP 7.0, MySQL.

Steps to reproduce

1. Run a full Data migration
2. Place orders on Magento 1
3. Run a Delta Data migration

Expected result

1. Delta completes successfully and you can see the orders in the Magento 2 Order Grid

Actual result

1. Delta migration fails returning an exception

[2018-10-26 07:49:52][INFO][mode: delta][stage: delta delivering][step: OrderGrids Step]: started
......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

  [Exception]
  Notice: Array to string conversion in /var/www/vhosts/pramworld.co.uk/production/releases/20181025171738/vendor/magento/data-migration-tool/src/Migration/ResourceModel/Adapter/Mysql.php on line 199

1. New Orders from M1 are not visible in the M2 order grid.

Additional notes

[victor-v-rad]

Thank you @DanCarlyon for reporting this issue and pull request. Internal ticket MAGETWO-96201 to process it