[21153, 21154] Address XMLDynamicParser Fuzzer regressions

[Mario-DL]

Description

This PR addresses some XML fuzzer regressions that affects DynamicTypes Parsing. It is for that reason that there are no backports. In summary, it was a non-captured std::out_of_range exception and a nullptr check missing. I tried also protecting analogous code snippets within the file.

Contributor Checklist

• Commit messages follow the project guidelines.
• The code follows the style guidelines of this project.
• Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally
• Any new/modified methods have been properly documented using Doxygen.
• Any new configuration API has an equivalent XML API (with the corresponding XSD extension)
• ❌ Changes are backport compatible: they do NOT break ABI nor change library core behavior.
• Changes are API compatible.
• NO New feature has been added to the versions.md file (if applicable).
• NO New feature has been documented/Current behavior is correctly described in the documentation.
• ❌ Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

[JesusPoderoso]

LGTM with green CI