An unmatched URL got routed accidentally

[clippit]

Issue Description

In some circumstances, an URL which should be an 404 matches a router. See code below.
It's really a critical bug as if someone write a DELETE handler and a vulnerable request could delete data through the router!

Checklist

• Dependencies installed
• No typos
• Searched existing issues and docs

Expected behaviour

http://localhost:1323/aaa => Hello from router 1!
http://localhost:1323/aaa/foo => Hello from router 2!
http://localhost:1323/aaa/bar => Hello from router 3!
http://localhost:1323/aaa/bbbbbb => Not Found

Actual behaviour

http://localhost:1323/aaa => Hello from router 1!
http://localhost:1323/aaa/foo => Hello from router 2!
http://localhost:1323/aaa/bar => Hello from router 3!
http://localhost:1323/aaa/bbbbbb => Hello from router 1! <--- wrong router!

Steps to reproduce

Define 4 routers as below, check the PoC code.

• /:param1
• /:param1/foo
• /:param1/bar
• /:param1/bar/:param2

Working code to debug

package main

import (
	"fmt"
	"net/http"

	"github.com/labstack/echo/v4"
	"github.com/labstack/echo/v4/middleware"
)

func main() {
	// Echo instance
	e := echo.New()

	// Middleware
	e.Use(middleware.Logger())
	e.Use(middleware.Recover())

	// Routes
	e.GET("/:param1", helloHandler(1))
	e.GET("/:param1/foo", helloHandler(2))
	e.GET("/:param1/bar", helloHandler(3))
	e.GET("/:param1/bar/:param2", helloHandler(4))

	// Start server
	e.Logger.Fatal(e.Start(":1323"))
}

// Handler
func helloHandler(id int) echo.HandlerFunc {
	return func(c echo.Context) error {
		return c.String(http.StatusOK, fmt.Sprintf("Hello from router %d!", id))
	}

}

Version/commit

4.1.6