Panic while using interface or []interface param type

[guning]

Describe the bug

Panic while using interface or []interface param type

To Reproduce

code:

type LogSearchRequest  struct {
	Size  int           `json:"size"`
	After []interface{} `json:"after"` // es cursor
        StartAt int64 `json:"start_at"`
        EndAt int64 `json:"end_at"`
}

// @Param request query LogSearchRequest true "query param"
func API()....

command: swag.exe init --pd

Expected behavior

...
2023/10/20 10:23:59 Generating syslogApi.LogSearchRequest
2023/10/20 10:23:59 Generating syslogApi.LogRequest
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x68 pc=0x13b1ba5]

goroutine 1 [running]:
github.com/swaggo/swag/v2.(*Operation).ParseParamComment(0xc036c0bd40, {0xc00062e46a, 0x3c}, 0x2?)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/operation.go:324 +0x1da5
github.com/swaggo/swag/v2.(*Operation).ParseComment(0xc036c0bd40, {0xc00062e460?, 0x1?}, 0xc02ac71440?)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/operation.go:143 +0x1c5
github.com/swaggo/swag/v2.(*Parser).ParseRouterAPIInfo(0xc000180000, 0xc000173e00)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/parser.go:1005 +0x214
github.com/swaggo/swag/v2.(*PackagesDefinitions).RangeFiles(0xc000115140, 0xc02ac71568)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/packages.go:107 +0x2ad
github.com/swaggo/swag/v2.(*Parser).ParseAPIMultiSearchDir(0xc000180000, {0xc000176b70?, 0x1?, 0x0?}, {0x159aa56?, 0x7?}, 0x221ca526558?)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/parser.go:427 +0x1f6
github.com/swaggo/swag/v2/gen.(*Gen).Build(0xc000114e70, 0xc00010cdc0)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/gen/gen.go:219 +0x79d
main.initAction(0xc0000ca9a0?)
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/cmd/swag/main.go:207 +0xb25
github.com/urfave/cli/v2.(*Command).Run(0xc0000ca9a0, 0xc000110980, {0xc00006a660, 0x6, 0x6})
        D:/guning/goruntime/modcache/github.com/urfave/cli/[email protected]/command.go:274 +0xa42
github.com/urfave/cli/v2.(*Command).Run(0xc0000cadc0, 0xc000110840, {0xc0000a4000, 0x7, 0x8})
        D:/guning/goruntime/modcache/github.com/urfave/cli/[email protected]/command.go:267 +0xc8a
github.com/urfave/cli/v2.(*App).RunContext(0xc0000003c0, {0x1681708?, 0xc000018190}, {0xc0000a4000, 0x7, 0x8})
        D:/guning/goruntime/modcache/github.com/urfave/cli/[email protected]/app.go:332 +0x605
github.com/urfave/cli/v2.(*App).Run(...)
        D:/guning/goruntime/modcache/github.com/urfave/cli/[email protected]/app.go:309
main.main()
        D:/guning/goruntime/modcache/github.com/swaggo/swag/[email protected]/cmd/swag/main.go:285 +0x5e6

Screenshots

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Your swag version

2.0.0-rc3

Your go version

1.18.10

Desktop (please complete the following information):

• OS: Windows11
• Browser:--
• Version:--

Additional context

I found that func getUnderlyingSchema returns nil when the underlay param type is "interface{}". Caller without nil checking will run into fatal panic.

https://github.com/swaggo/swag/blob/master/operation.go#L310
https://github.com/swaggo/swag/blob/master/operation.go#L330