LTR Retriever crashes when input assembly does not contain LTRs

[GallVp]

Description of the bug

LTR Retriever crashes when input assembly does not contain LTRs

Command used and terminal output

No response

Relevant files

No response

System information

No response

[GallVp]

Tasks to gracefully handle assemblies for which no LTRs are found:

• Add unit tests to FASTA_LTRRETRIEVER_LAI relevant modules to verify that they can exit gracefully
  • ltrfinder: Added test to verify graceful handling of no ltr input nf-core/modules#5979
  • ltrharvest: Added test to verify graceful handling of no ltr input nf-core/modules#5978
  • ltrretriever/ltrretriever: Added test to verify graceful handling of … nf-core/modules#5980
• Add a pipeline level test to verify that FASTA_LTRRETRIEVER_LAI passes an appropriate log to the reporting module which is then displayed in the report.html

See patch PR: #106