Error 'Object not set to an instance of an object' when trying to open data map in EngageOne Designer

EngageOne Designer 6.0.x
 

Issue

Receiving the following error when trying to open a data map:

In 6.0.1242, the error is:

"Object not set to an instance of an object"

In 6.0.1564, the error is:

Unable to load the Data Map The Dictionary does not contain all of the Data Map aliases Please contact customer support.

Cause

The error is caused by deleting aliases in the dictionary that are used by the data map.

Resolution

UPDATED: July 10, 2019
This has been fixed with a SQL script (quote ref DOC-6685)