Fix a crash by auth commands when online

telegram/commands.go

@@ -259,6 +259,10 @@ func (c *Client) ProcessTransportCommand(cmdline string, resource string) string
 			return telegramNotInitialized
 		}
 
+		if c.authorizer.isClosed {
+			return "Authorization is done already"
+		}
+
 		switch cmd {
 		// sign in
 		case "login":
@@ -290,7 +294,7 @@ func (c *Client) ProcessTransportCommand(cmdline string, resource string) string
 	// cancel auth
 	case "cancelauth":
 		if c.Online() {
-			return "Not allowed when online"
+			return "Not allowed when online, use /logout instead"
 		}
 		c.cancelAuth()
 		return "Cancelled"