If the mount point is abnormal, the debug command cannot obtain the config file

[YunhuiChen]

What happened:
1、kill redis
2、2024/05/17 10:46:40.879406 juicefs[2490094] : failed to read config file: open /juicefs1/.jfs.config: input/output error [debug.go:134]
2024/05/17 10:46:40.879496 juicefs[2490094] : failed to unmarshal config file: unexpected end of JSON input [debug.go:138]
2024/05/17 10:47:02.867643 juicefs[2490094] : Failed to collect special file: failed to get volume config .jfs.config: signal: killed [debug.go:602]

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?

Environment:

• JuiceFS version (use juicefs --version) or Hadoop Java SDK version:
• Cloud provider or hardware configuration running JuiceFS:
• OS (e.g cat /etc/os-release):
• Kernel (e.g. uname -a):
• Object storage (cloud provider and region, or self maintained):
• Metadata engine info (version, cloud provider managed or self maintained):
• Network connectivity (JuiceFS to metadata engine, JuiceFS to object storage):
• Others:

[YunhuiChen]

Same situation at.stats