fix: ensure output buffer is closed after use of command()

[paulbalandan]

Description
When the command run through command() throws, output buffering is not closed, causing risky tests in phpunit.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[michalsn]

Looks good, but we need a changelog entry.

[paulbalandan]

Looks good, but we need a changelog entry.

Thanks. Added changelog.