Fix crash when the markdown table summary is empty

[nvuillam]

Fixes #5358

[github-actions]

🦙 MegaLinter status: ⚠️ WARNING

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ API	spectral	1		0	0	1.81s
⚠️ BASH	bash-exec	6		1	0	0.02s
✅ BASH	shellcheck	6		0	0	0.13s
✅ BASH	shfmt	6	0	0	0	0.52s
✅ COPYPASTE	jscpd	yes		no	no	2.76s
✅ DOCKERFILE	hadolint	131		0	0	28.66s
✅ JSON	jsonlint	20		0	0	0.18s
✅ JSON	v8r	22		0	0	14.47s
⚠️ MARKDOWN	markdownlint	269	0	304	0	21.4s
✅ MARKDOWN	markdown-table-formatter	269	0	0	0	138.62s
⚠️ PYTHON	bandit	219		67	0	4.41s
✅ PYTHON	black	219	0	0	0	4.83s
✅ PYTHON	flake8	219		0	0	1.92s
✅ PYTHON	isort	219	0	0	0	1.33s
✅ PYTHON	mypy	219		0	0	11.41s
✅ PYTHON	pylint	219		0	0	21.86s
✅ PYTHON	ruff	219	0	0	0	0.81s
✅ REPOSITORY	checkov	yes		no	no	36.6s
✅ REPOSITORY	git_diff	yes		no	no	0.51s
⚠️ REPOSITORY	grype	yes		27	no	33.72s
✅ REPOSITORY	secretlint	yes		no	no	8.86s
✅ REPOSITORY	syft	yes		no	no	2.57s
✅ REPOSITORY	trivy	yes		no	no	10.06s
✅ REPOSITORY	trivy-sbom	yes		no	no	21.75s
✅ REPOSITORY	trufflehog	yes		no	no	4.41s
✅ SPELL	cspell	727		0	0	13.99s
⚠️ SPELL	lychee	351		32	0	40.18s
✅ XML	xmllint	3	0	0	0	1.35s
✅ YAML	prettier	160	0	0	0	3.66s
✅ YAML	v8r	103		0	0	23.87s
✅ YAML	yamllint	161		0	0	3.73s

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