Fix protected branch using IssueID (#9348)

Signed-off-by: jolheiser <john.olheiser@gmail.com>

models/branches.go

@@ -153,7 +153,7 @@ func (protectBranch *ProtectedBranch) HasEnoughApprovals(pr *PullRequest) bool {
 
 // GetGrantedApprovalsCount returns the number of granted approvals for pr. A granted approval must be authored by a user in an approval whitelist.
 func (protectBranch *ProtectedBranch) GetGrantedApprovalsCount(pr *PullRequest) int64 {
-	approvals, err := x.Where("issue_id = ?", pr.Issue.ID).
+	approvals, err := x.Where("issue_id = ?", pr.IssueID).
 		And("type = ?", ReviewTypeApprove).
 		And("official = ?", true).
 		Count(new(Review))