[MM-56061] Only render where field in model.AppError when it's present (#25648)

* Only render where field in model.AppError when it's present

* Remove trailing comma from permission error

server/channels/app/post.go

@@ -2055,10 +2055,10 @@ func (a *App) GetPostIfAuthorized(c request.CTX, postID string, session *model.S
 	if !a.SessionHasPermissionToChannel(c, *session, channel.Id, model.PermissionReadChannelContent) {
 		if channel.Type == model.ChannelTypeOpen && !*a.Config().ComplianceSettings.Enable {
 			if !a.SessionHasPermissionToTeam(*session, channel.TeamId, model.PermissionReadPublicChannel) {
-				return nil, a.MakePermissionError(session, []*model.Permission{model.PermissionReadPublicChannel})
+				return nil, model.MakePermissionError(session, []*model.Permission{model.PermissionReadPublicChannel})
 			}
 		} else {
-			return nil, a.MakePermissionError(session, []*model.Permission{model.PermissionReadChannelContent})
+			return nil, model.MakePermissionError(session, []*model.Permission{model.PermissionReadChannelContent})
 		}
 	}