Incorrect code coverage report when all lines are covered

## Description

Code coverage report generated by `c8` is showing incorrect result despite all branches are covered.

I even tested it with compiled JavaScript files by `swc` and the result remains unchanged when there is no additional code generated found at the said line.

## Actual behavior


There is 1 additional branch has been reported not being covered.

## Expected behavior


All lines are covered and `c8` should be able to pick up the result correctly.

## Reproduction steps

1. [reduced test case](https://github.com/motss/c8-code-coverage-bug)

## Reqeuired info

* **c8**: `7.7.3`
* **Version**: `node@16.5.0`
* **Platform**: `Windows 10 x64`