if milestone id is zero don't get it from database (#7169)

routers/repo/issue.go

@@ -426,6 +426,7 @@ func NewIssue(ctx *context.Context) {
 	ctx.Data["BodyQuery"] = body
 
 	milestoneID := ctx.QueryInt64("milestone")
+	if milestoneID > 0 {
 		milestone, err := models.GetMilestoneByID(milestoneID)
 		if err != nil {
 			log.Error("GetMilestoneByID: %d: %v", milestoneID, err)
@@ -433,6 +434,7 @@ func NewIssue(ctx *context.Context) {
 			ctx.Data["milestone_id"] = milestoneID
 			ctx.Data["Milestone"] = milestone
 		}
+	}
 
 	setTemplateIfExists(ctx, issueTemplateKey, IssueTemplateCandidates)
 	renderAttachmentSettings(ctx)