Remove checkIfExists from interop file resolution

[delfiterradas]

PR checklist

Required for nf-core/demultiplex#378

• 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 module conventions in the contribution docs
• If necessary, include test data in your PR.
• Remove all TODO statements.
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• Use BioConda and BioContainers if possible to fulfil software requirements.
• Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
  • For modules:
    • nf-core modules test <MODULE> --profile docker
    • nf-core modules test <MODULE> --profile singularity
    • nf-core modules test <MODULE> --profile conda
  • For subworkflows:
    • nf-core subworkflows test <SUBWORKFLOW> --profile docker
    • nf-core subworkflows test <SUBWORKFLOW> --profile singularity
    • nf-core subworkflows test <SUBWORKFLOW> --profile conda

[SPPearce]

Why do you not want to check the files exist?

[delfiterradas]

Why do you not want to check the files exist?

@SPPearce Because there is a test that fails in the demultiplex pipeline because the input doesn't have InterOp files. However, if we remove the check, multiqcsav can still work without this file and can create the report