Reason why Global Search showing (null) Beside the Transaction Name and Number

When searching for transactions using Global Search the quick results will display the transaction name followed by the customer/vendor name in parenthesis:

There might be results displayed as Transaction Name/ID (null) and the reasons for that can be:

1. Per design the given transaction type doesn't have a Customer entity such as:
   Assembly Build 
   Inventory Worksheet 
   Inventory Adjustment 
   Journal 
   Transfer Order 
2. The transaction has a Customer field defined but it has been created without selecting a customer entity