[Bug] panic: reflect: call of reflect.Value.NumField on int Value

[seamounts]

Problem Description

看的应该是对非结构体类型（比如 int） 调用 reflect.Value.NumField() 方法，导致 panic

panic: reflect: call of reflect.Value.NumField on int Value
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: goroutine 5488290 [running]:
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: reflect.flag.mustBe(...)
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]:         /opt/hostedtoolcache/go/1.24.0/x64/src/reflect/value.go:218
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: reflect.Value.NumField({0x1a8a9e0?, 0xc000c182a0?, 0x1a40a60?})
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]:         /opt/hostedtoolcache/go/1.24.0/x64/src/reflect/value.go:1852 +0x85
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: github.com/containerd/nydus-snapshotter/config/daemonconfig.serializeWithSecretFilter({0x1a8a9e0, 0xc000c182a0})
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]:         /home/runner/work/nydus-snapshotter/nydus-snapshotter/config/daemonconfig/daemonconfig.go:201 +0x1bb
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: github.com/containerd/nydus-snapshotter/config/daemonconfig.serializeWithSecretFilter({0x1c52120, 0xc0003cd630})
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]:         /home/runner/work/nydus-snapshotter/nydus-snapshotter/config/daemonconfig/daemonconfig.go:232 +0x5f4
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: github.com/containerd/nydus-snapshotter/config/daemonconfig.DumpConfigFile({0x1c52120?, 0xc0003cd630?}, {0xc0005cec00, 0x5e})
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]:         /home/runner/work/nydus-snapshotter/nydus-snapshotter/config/daemonconfig/daemonconfig.go:134 +0x45
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]: github.com/containerd/nydus-snapshotter/config/daemonconfig.(*FuseDaemonConfig).DumpFile(0xc0003cd630, {0xc0005cec00, 0x5e})
Nov 03 14:03:18 bk8s6-5 containerd-nydus-grpc[3480425]:         /home/runner/work/nydus-snapshotter/nydus-snapshotter/config/daemonconfig/fuse.go:106 +0x58
......

// Used when nydusd works as a FUSE daemon or vhost-user-fs backend
type FuseDaemonConfig struct {
        ......
	AmplifyIo       *int          `json:"amplify_io,omitempty"`
	......
}

How to reproduce

snapshotter 使用 0.15.7，配置如下：开启 enable_backend_source

[experimental]
# Whether to enable authentication support
# The option enables nydus snapshot to provide backend information to nydusd.
enable_backend_source = true

[imeoer]

Thanks for the report, the enable_backend_source option is used to let nydusd request the snapshotter to dynamically update registry auth, this is an experimental feature, and we later found that the implementation isn't ideal, it may be removed in the future.