Search Forms; Does Not Equal is not working correctly for optional string fields

Search forms
When searching on optional string fields (e.g. Account.Ledger) the 'Equals' and 'Does Not Equal' were not working correctly.
This will applied to all search forms for search fields that are not mandatory fields.

E.g.; Account Search
1. Ledger Does Not Equal Value
This will now bring back all Accounts that do not equal the value entered including those that have null in the field
If is entered as the value then all Accounts that have a value entered will be returned

2. Ledger Equals Value
If is entered as the value then Accounts that do not have a value entered for Ledger will be returned.