Fix multiqc_title param missing --title flag

[mcmero]

Fixes the fallback for the multiqc_title parameter (missing --title flag). If multiqc_title is not provided, currently leads to the following error in MultiQC:

╭─ Error ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ Invalid value for '[ANALYSIS DIRECTORY]': Path 'MultiQC' does not exist.                                                                                                                                                                                                                                                 │
╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

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!
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