Empty arguments for issueFunctions JQL

Steps to reproduce: 

• Go to Issues > Search for Issues
• In basic view, click on More and select issueFunction
• Add Function
• Select 'hasLinks' from function dropdown
• Leave link desc blank
• Add +2 to number of links

This bug also covers using hasAttachments if you don't enter a type and enter +2 in the number of.

Expected Behaviour: 

When clicking Add function, results should be returned for issue with more than 2 link type of any type. 

When clicking Add function, results should be returned for issue with more than 2 attachments of any type. 

Actual Behaviour:

When clicking Add function, an error is returned (see attached) so the function cannot be used unless you select a link type from the dropdown. As the link type dropdown is not mandatory you should be able to add the function without selecting a value. 

If you perform the same steps above but select a link type, the function can be added without error. 

If you leave the number of field blank but select a link type, the function can be added without an error.