Fix: check-log panic with invalid memory address or nil pointer dereference

[ne-sachirou]

I created the patch #823 , but this patch has a bug.

Procedure for reproducing :

• Apply this patch.

  diff --git a/check-log/lib/check-log.go b/check-log/lib/check-log.go
  index f942c58..2efa68e 100644
  --- a/check-log/lib/check-log.go
  +++ b/check-log/lib/check-log.go
  @@ -16,6 +16,7 @@ import (
          "regexp"
          "strconv"
          "strings"
  +       "time"
  
          "github.com/jessevdk/go-flags"
          "github.com/mackerelio/checkers"
  @@ -566,6 +567,8 @@ var errFileNotFoundByInode = fmt.Errorf("old file not found")
  
   func findFileByInode(inode uint, dir string) (string, error) {
          entries, readDirErr := os.ReadDir(dir)
  +       fmt.Println("sleeping")
  +       time.Sleep(10 * time.Second)
          for _, entry := range entries {
                  fi, err := entry.Info()
                  if err != nil && !errors.Is(err, os.ErrNotExist) {

• Create a log file. touch dummy.log
• Create a state file. go run main.go -f ./dummy.log -p error -s $(pwd)
• Rotate the log file. mv dummy.log dummy-1.log && touch dummy.log
• Run check-log. go run main.go -f ./dummy.log -p error -s $(pwd)
• When the "sleeping" is printed, remove the rotated log file. rm dummy-1.log
• panic

[Arthur1]

👍