Fixed parameter manager for Monte Carlo runs

[mrvisscher]

Fixed an issue where the MCParameterManager couldn't deal properly with the changed ParameterManager class of last update.

• fixes Attribute error running Montecarlo analysis including parameters #1424

Checklist

• Keep pull requests small so they can be easily reviewed.
• Update the documentation
  • For in-code documentation, please follow the numpy style guide.
  • For user documentation, please update the wiki in
    ./activity_browser/docs/wiki
• Update tests.
• Link this PR to related issues by using closing keywords.

If you have write access (otherwise a maintainer will do this for you):

• Categorize the PR by setting a good title and adding one of the labels:
  bug, feature, ui, change, documentation, breaking, ci
  as they show up in the changelog.
• Add a milestone to the PR (and related issues, if any) for the intended release.
• Request a review from another developer.

[coveralls]

coverage: 53.134% (+0.006%) from 53.128%
when pulling e98bf97 on mrvisscher:fix-paramter-mc
into 3da042e on LCA-ActivityBrowser:main.