tls config MinVersion rule causes panic

[erraggy]

Summary

Since version v2.9.1, the gosec rule for tls config's MinVersion will now panic at:
https://github.com/securego/gosec/blob/v2.9.1/rules/tls.go#L92

Steps to reproduce the behavior

You can use the following example go source:

package example

import (
	"crypto/tls"
	"fmt"
)

func causeGosecPanic(foo bool) {
	var minVer uint16

	if foo {
		minVer = tls.VersionTLS12
	} else {
		minVer = 1
	}

	cfg := tls.Config{
		MinVersion: minVer,
	}
	fmt.Println("tls min version", cfg.MinVersion)
}

gosec version

v2.9.1

Go version (output of 'go version')

go1.16.9 darwin/amd64

Operating system / Environment

macOS Version 10.15.7

Expected behavior

no panic

Actual behavior

% gosec example/...
[gosec] 2021/11/05 17:08:04 Including rules: default
[gosec] 2021/11/05 17:08:04 Excluding rules: default
[gosec] 2021/11/05 17:08:04 Import directory: /Users/rcoleman/code/gosec_issue/example
[gosec] 2021/11/05 17:08:05 Checking package: example
[gosec] 2021/11/05 17:08:05 Checking file: /Users/rcoleman/code/gosec_issue/example/tls_min_version_panic.go
panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
github.com/securego/gosec/v2/rules.(*insecureConfigTLS).processTLSConfVal(0xc00048c600, 0xc0002edc20, 0xc0001a6070, 0x143ac01)
	/Users/rcoleman/sdk/modcache/github.com/securego/gosec/v2@v2.9.1/rules/tls.go:92 +0xaf4
github.com/securego/gosec/v2/rules.(*insecureConfigTLS).Match(0xc00048c600, 0x143a530, 0xc0004f0e00, 0xc0001a6070, 0x168b800, 0x0, 0x1)
	/Users/rcoleman/sdk/modcache/github.com/securego/gosec/v2@v2.9.1/rules/tls.go:183 +0x158
github.com/securego/gosec/v2.(*Analyzer).Visit(0xc0000720c0, 0x143a530, 0xc0004f0e00, 0x1438a20, 0xc0000720c0)
	/Users/rcoleman/sdk/modcache/github.com/securego/gosec/v2@v2.9.1/analyzer.go:375 +0x40d
go/ast.Walk(0x1438a20, 0xc0000720c0, 0x143a530, 0xc0004f0e00)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:52 +0x63
go/ast.walkExprList(0x1438a20, 0xc0000720c0, 0xc00059e5d0, 0x1, 0x1)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:26 +0x9e
go/ast.Walk(0x1438a20, 0xc0000720c0, 0x143a300, 0xc0004f0e40)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:207 +0x1f97
go/ast.walkStmtList(0x1438a20, 0xc0000720c0, 0xc0004f0e80, 0x4, 0x4)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:32 +0x9e
go/ast.Walk(0x1438a20, 0xc0000720c0, 0x143a3f0, 0xc0002edc50)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:224 +0x1968
go/ast.Walk(0x1438a20, 0xc0000720c0, 0x143a6c0, 0xc0002edc80)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:344 +0xce6
go/ast.walkDeclList(0x1438a20, 0xc0000720c0, 0xc0004ef8e0, 0x2, 0x2)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:38 +0x9e
go/ast.Walk(0x1438a20, 0xc0000720c0, 0x143a670, 0xc000257100)
	/Users/rcoleman/sdk/go1.16.9/src/go/ast/walk.go:353 +0x2446
github.com/securego/gosec/v2.(*Analyzer).Check(0xc0000720c0, 0xc0003f1680)
	/Users/rcoleman/sdk/modcache/github.com/securego/gosec/v2@v2.9.1/analyzer.go:231 +0x518
github.com/securego/gosec/v2.(*Analyzer).Process(0xc0000720c0, 0x0, 0x0, 0x0, 0xc0000a30c0, 0x1, 0x1, 0x1, 0x0)
	/Users/rcoleman/sdk/modcache/github.com/securego/gosec/v2@v2.9.1/analyzer.go:154 +0x149
main.main()
	/Users/rcoleman/sdk/modcache/github.com/securego/gosec/v2@v2.9.1/cmd/gosec/main.go:375 +0x82b