Cast empty headers to int

[ahmedash95]

Hello Patrick,

1️⃣ Why should it be added? What are the benefits of this change?
Fixes #3563. also, it makes handling empty headings to have unique value instead of having all as an empty string

2️⃣ Does it contain multiple, unrelated changes? Please separate the PRs out.
Nope.

3️⃣ Does it include tests, if possible?
Yes

4️⃣ Any drawbacks? Possible breaking changes?
It might break existing projects if any rely on the empty value of the headings

5️⃣ Mark the following tasks as done:

• Checked the codebase to ensure that your feature doesn't already exist.
• Take note of the contributing guidelines.
• Checked the pull requests to ensure that another person hasn't already submitted a fix.
• Added tests to ensure against regression.
• Updated the changelog

6️⃣ Thanks for contributing! 🙌

[patrickbrouwers]

Thanks!