Add trycatch to enrichment plots

[WackerO]

For pathway analyses where many pathways are enriched, the ggsave function throws an error when trying to save the enrichment plots. This PR adds trycatches to allow the pipeline to continue; the plots are in such a case not saved

PR checklist

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added a new tool - have you followed the pipeline conventions in the contribution docs
• Make sure your code lints (nf-core lint).
• Ensure the test suite passes (nextflow run . -profile test,docker --outdir <OUTDIR>).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).

[mapo9]

lgtm