Avoid crash when adding ontologies if not a proper meta.yml

[toniher]

I noticed the problem when running:

 nf-core -v modules lint --fix diamond/blastp

It simply presents a warning pointing to the involved channel and elements.

[codecov]

Codecov Report

Attention: Patch coverage is 30.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 76.95%. Comparing base (6421bab) to head (37018cc).
Report is 7 commits behind head on dev.

Files with missing lines	Patch %	Lines
nf_core/modules/lint/__init__.py	30.00%	7 Missing ⚠️

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[toniher]

@nf-core-bot fix linting

[mirpedrol]

LGTM, thanks!