Removing issue type from issue type scheme that's associated with a request type will throw 'Request type does not exist' error

Summary

If you remove an issue type from the issue type scheme that's associated with a request type in Service Desk then that request type will still be visible in the customer portal, but it will throw the error 'Request type does not exist'

Steps to Reproduce

1. Create a request type mapped with an issue type
2. Remove that issue type from the issue type scheme associated with that project
3. Try to create an issue with that request type

Expected Results

Request type shouldn't be there

Actual Results

The request type is present, and when clicking it you get the error 'Request type does not exist'

Workaround

Run the following query to identify all issue types mapped to request types that aren't in the relevant issue type scheme. You can then add the issue type back to the issue type scheme and then remove the request type from the project. You can then remove the issue types once more.

select p.pkey as project_key, i.pname as issue_type_name, f."NAME" as portal_name from project p, "AO_54307E_VIEWPORTFORM" f, "AO_54307E_VIEWPORT" v, issuetype i where f."VIEWPORT_ID" = v."ID" and v."PROJECT_ID" = p.id and i.id::int = f."ISSUE_TYPE_ID" and p.projecttype = 'service_desk' and (p.pkey, i.id) not in (select p.pkey, i.id from project p, issuetype i, configurationcontext c, optionconfiguration o where p.id = c.project and c.fieldconfigscheme = o.fieldconfig and o.optionid = i.id and c.customfield = 'issuetype') and p.id in (select project from configurationcontext where customfield = 'issuetype') order by pkey asc;