`vep_plugin_files` listed as optional parameter but pipeline won't run without it

### Description of the bug

`vep_plugin_files` listed as optional parameter but pipeline won't run without it

### Command used and terminal output

```console
ERROR ~ No such variable: ch_vep_extra_files

 -- Check script './workflows/raredisease.nf' at line: 516 or see '.nextflow.log' file for more details
```


### Relevant files

_No response_

### System information

_No response_