Fixed parser crashes on a sequence right after the directives end marker

[fktn-k]

The fkYAML parser in the latest develop branch crashes with the following valid YAML snippets (taken from the official YAML test suite Z9M4/in.yaml):

%TAG !e! tag:example.com,2000:app/
---
- !e!foo "bar"

After some investigation, it's turned out that the parser doesn't process directive end markers (denoted with ---) properly.
So, this PR has fixed the parser's issue and added a test case to validate the change.

Pull Request Checklist

Read the CONTRIBUTING.md file for detailed information.

• Changes are described in the pull request or in a referenced issue.
• The test suite compiles and runs without any error.
• The code coverage on your branch is 100%.
• The documentation is updated if you added/changed a feature.

Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
• Please refrain from proposing changes that would break YAML specifications. If you propose a conformant extension of YAML to be supported by the library, please motivate this extension.
• Please do not open pull requests that address multiple issues.

[github-actions]

Upload Coverage Event Notification

Coverage data has been uploaded for the commit 4afb6ed81da0d8f233979b70bf0864c8175905ba.
You can download the artifact which contains the same file uploaded to the Coveralls and its HTML version.

Name	fkYAML_coverage.pr327.zip
ID	1453640802
URL	https://github.com/fktn-k/fkYAML/actions/runs/8862167742/artifacts/1453640802

[coveralls]

Pull Request Test Coverage Report for Build 8862167742

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 8860575999:	0.0%
Covered Lines:	3541
Relevant Lines:	3541

---

💛 - Coveralls