resolve tree-view not able to open activity correctly

[marc-vdm]

Checklist

• Keep pull requests small so they can be easily reviewed.
• Update the documentation, please follow the numpy style guide.
• Update tests.
• 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.
• Link this PR to related issues by using closing keywords.
• Add a milestone to the PR (and related issues, if any) for the intended release.
• Request a review from another developer.

[coveralls]

coverage: 54.477%. remained the same
when pulling 208f5cf on marc-vdm:db_tree_view_patch
into ab9cdaa on LCA-ActivityBrowser:main.

[coveralls]

coverage: 54.476% (-0.001%) from 54.477%
when pulling e0f14dc on marc-vdm:db_tree_view_patch
into ab9cdaa on LCA-ActivityBrowser:main.

[coveralls]

coverage: 54.447% (-0.03%) from 54.477%
when pulling e0f14dc on marc-vdm:db_tree_view_patch
into ab9cdaa on LCA-ActivityBrowser:main.

[mrvisscher]

lgtm!