fix: missing entries in selection view

[lars-reimann]

Closes #270.

Summary of Changes

Show entries in the selection view even when they don't have children. When filtering, entries only get removed when we filter at a lower API level, i.e. we keep all

• modules that match the filter if we only filter modules (e.g., module:_min_ finds the empty module sklearn._min_dependencies).
• classes that match the filter if we only filter modules or classes (e.g., class:ArffCon finds the empty class ArffContainerType).
• functions that match the filter if we only filter modules, classes, or parameters (e.g., function:get_con finds the parameterless function get_config.

Testing instructions

1. Check that the selection view contains entries without children when no filter is set.
2. Try the examples given above and others of the same category.
3. Check that non-matching entries are still removed properly when filtering.

[github-actions]

Mega-Linter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	1.7s
✅ GIT	git_diff	yes		no	0.01s
✅ TSX	eslint	3	0	0	12.83s
✅ TYPESCRIPT	eslint	5	0	0	12.33s
✅ TYPESCRIPT	prettier	8	0	0	2.41s

See errors details in artifact Mega-Linter reports on GitHub Action page
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

[paul0314]

lgtm