Fix internal sever error when visiting a PR that bound to the deleted team (#24127)

Close: #23738

The actual cause of `500 Internal Server Error` in the issue is not what
is descirbed in the issue.

The actual cause is that after deleting team, if there is a PR which has
requested reivew from the deleted team, the comment could not match with
the deleted team by `assgin_team_id`. So the value of `.AssigneeTeam`
(see below code block) is `nil` which cause `500 error`.


https://github.com/go-gitea/gitea/blob/1c8bc4081a4f4d0d921ac218cb724ce97924d410/templates/repo/issue/view_content/comments.tmpl#L691-L695

To fix this bug, there are the following problems to be resolved:

- [x] 1. ~~Stroe the name of the team in `content` column when inserting
`comment` into DB in case that we cannot get the name of team after it
is deleted. But for comments that already exist, just display "Unknown
Team"~~ Just display "Ghost Team" in the comment if the assgined team is
deleted.
- [x] 2. Delete the PR&team binding (the row of which `review_team_id =
${team_id} ` in table `review`) when deleting team.
- [x] 3.For already exist and undeleted binding rows in in table
`review`, ~~we can delete these rows when executing migrations.~~ they
do not affect the function, so won't delete them.

0 files changed, 0 insertions, 0 deletions