Fixing permalinks to channels your not a memeber of (#2805)

api/command_join.go

@@ -46,7 +46,7 @@ func (me *JoinProvider) DoCommand(c *Context, channelId string, message string)
 					return &model.CommandResponse{Text: c.T("api.command_join.fail.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
 				}
 
-				JoinChannel(c, v.Id, "")
+				JoinChannelById(c, c.Session.UserId, v.Id)
 
 				if c.Err != nil {
 					c.Err = nil