fix: incorrectly calculating the size of script that is loaded from memory

[hulxv]

Description

Fixes #513

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Documentation update

Checklist:

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests/screenshots (if any) that prove my fix is effective or that my feature works.
• I have tested the tests implicated (if any) by my own code and they pass (make test or ctest -VV -R <test-name>).
• If my change is significant or breaking, I have passed all tests with ./docker-compose.sh test &> output and attached the output.
• I have tested my code with OPTION_BUILD_ADDRESS_SANITIZER or ./docker-compose.sh test-address-sanitizer &> output and OPTION_TEST_MEMORYCHECK.
• I have tested my code with OPTION_BUILD_THREAD_SANITIZER or ./docker-compose.sh test-thread-sanitizer &> output.
• I have tested with Helgrind in case my code works with threading.
• I have run make clang-format in order to format my code and my code follows the style guidelines.

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[hulxv]

@devraymondsh @viferga

[devraymondsh]

@hulxv
LGTM. Approved.