False positive when checking slice length

[QianKuang8]

Case 2 would cause an error in Nilaway. IMO, it looks like a false positive case.

package main

import "fmt"

func main() {
	var data []int
	// case 1: OK
	if len(data) == 1 {
		fmt.Println(data[0])
	}

	// case 2: Not OK
	length := len(data)
	if length == 1 {
		fmt.Println(data[0])
	}
}

// error: Potential nil panic detected. Observed nil flow from source to dereference point: 
// unassigned variable `data` sliced into