fix: in fixpath case, wildcard node should be the last child.

[liruohrh]

define {prefix}/{param path like :id} and {prefix}/, and than access no defined path like {prefix}/... will panic for panic("invalid node type"). for it didn't obtain the wildcard child node correctly.

here is a example case. after start server, access http://localhost:8080/prefix/a/b/c , will cause panic.

package main

import (
	"errors"
	"net/http"

	"github.com/gin-gonic/gin"
)

func main() {
	r := gin.Default()
	r.RedirectFixedPath = true
	r.GET("/prefix/:id", func(c *gin.Context) {
		c.JSON(200, "id")
	})
	r.GET("/prefix/xxx", func(c *gin.Context) {
		c.JSON(200, "xxx")
	})
	if err := r.Run(":8080"); err != nil && errors.Is(err, http.ErrServerClosed) {
		panic(err)
	}
}

[appleboy]

Please add unit testing for the cause.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 98.81%. Comparing base (3dc1cd6) to head (deb81c1). :warning: Report is 194 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4394      +/-   ##
==========================================
- Coverage   99.21%   98.81%   -0.40%     
==========================================
  Files          42       44       +2     
  Lines        3182     3467     +285     
==========================================
+ Hits         3157     3426     +269     
- Misses         17       30      +13     
- Partials        8       11       +3     

Flag	Coverage Δ
	?
--ldflags="-checklinkname=0" -tags sonic	98.80% <100.00%> (?)
-tags go_json	98.75% <100.00%> (?)
-tags nomsgpack	98.80% <100.00%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	?
go-1.24	98.81% <100.00%> (?)
go-1.25	98.81% <100.00%> (?)
macos-latest	98.81% <100.00%> (-0.40%)	:arrow_down:
ubuntu-latest	98.81% <100.00%> (-0.40%)	:arrow_down:

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[liruohrh]

Please add unit testing for the cause.

Sorry, I thought such a small point didn't need to add tests. I added a test situation on the basis of the original test function. This test situation will cause panic before the error is fixed.