fix(mods): stop Manage Mods going blank on a null tag from the mod database

[Pixnop]

Part of #370, the blank Manage Mods page reported by Vinni_Pukh, b0b4444 and Villoch on the mod database listing and by a friend of NekoJess on the Discord within eleven hours of beta.7. This is the hotfix for the crash itself; the error boundary (#372) and the boundary validation named in the issue follow separately.

What broke

installedModTags in src/domain/mods/installedFilters.ts, new in #348, collects every _mod.tags entry across the installed mods and folds case with toLowerCase() during the first render of the page. The mod database's detail endpoint returns ["Cosmetics", "Crafting", "Storage", null] for Vanilla Variants, a very popular mod. null.toLowerCase() threw, and with no error boundary in the renderer, React unmounted the whole tree. Reproduced against the live API, not a fixture:

TypeError: Cannot read properties of null (reading 'toLowerCase')
  uniqueIgnoringCase src/domain/mods/installedFilters.ts:37
  installedModTags   src/domain/mods/installedFilters.ts:55

The list endpoint (/api/mods) is clean across all 8371 mods; the detail endpoint the launcher actually reads is the one that carries the null. The hand-written fixtures followed the documented shape, which is why the suite was green.

The fix

One helper, textEntries, keeps only string entries and reads a field that is not a list as empty, and every reader in the module goes through it: authors, category tags, and each release's game-version tags, on both the option-list side and the matcher side. A second helper, releasesOf, reads the releases list the same way and, after review, also drops entries that are not objects: { releases: [null] } passed the outer array check and release.tags then threw on the entry, the same crash class. Nothing in the module trusts the shape any more.

Tests

Six cases built from the real shape rather than a sanitised one: a null among the category tags (Vanilla Variants exactly), a null inside a release's tags, a non-string author, a tags field that is a string, a releases field that is a string rather than null (on purpose, null ?? [] reads as empty by accident and the guard has to hold for anything that is not a list), and a null entry inside an otherwise valid releases list.

Mutants, each applied alone against the committed tree and restored after:

Mutant	Result
textEntries keeps every entry, no string filter	red, 3 tests, the production TypeError verbatim
releasesOf drops the array guard for ?? []	red, the string-releases case
releasesOf drops the per-entry object filter	red, the [null] case, Cannot read properties of null (reading 'tags')

Testing

On head 86e2dd7:

• npm run typecheck: passed (node, web, tests).
• npm run lint:ci: 0 errors, 15 pre-existing React Hooks warnings.
• npm run format:check: passed.
• npm run test:coverage: 161 files, 2029 passed, 2 skipped; 93.4% statements, 90.2% branches, 92.68% functions, 94.96% lines locally, floors 87 / 85 / 85 / 89. The CI run on this head is the reference figure if the two differ by a hundredth.
• npm run build:unpack: passed, Electron 44.1.1 Linux.
• npx vitest run tests/domain/mods/installedFilters.test.ts: 28 passed.

Related issues

• Manage Mods goes blank when a ModDB listing carries a null category tag #370 (part 1 of 3: the crash; fix(renderer): contain a page render throw and get it into the log #372 is part 2)
• feat(mods): add author, tag and version filters to the Manage Mods page #348, which introduced the derivations
• fix(versions): extract a version token from probe output instead of storing the whole line #314, the same class of fix for the versions catalog

Type

• Bug fix
• Feature
• Performance
• Refactor or cleanup
• Tests only
• Docs or build

Checklist

• Targets dev, not main.
• npm run typecheck passes.
• npm run lint:ci passes.
• npm run format:check passes.
• npm run test:coverage passes, coverage at or above the floor in vitest.config.ts.
• npm run build:unpack passes.

[Zaldaryon]

Request changes

The fix correctly filters non-string tag and author entries, and the reported Vanilla Variants payload is covered. One malformed ModDB shape still crashes the same filter path: a null entry inside the otherwise valid releases array. The inline comment identifies the exact dereference and requested correction.

Please also complete the repository template evidence by marking npm run build:unpack in the checklist and adding the Testing and Related issues sections. The remote build and all required checks are green, but the PR description should record the commands and link #370 directly.

Verification

• Local npm ci: passed with 0 reported vulnerabilities.
• Local npm run typecheck: passed.
• Local npm run lint:ci: passed with 15 existing React Hooks warnings and 0 errors.
• Local npm run format:check: passed.
• Local npm run test:coverage: 161 files passed, 2,028 tests passed, 2 skipped; 93.40% statements, 90.20% branches, 92.68% functions, and 94.96% lines.
• Focused installedFilters.test.ts: 27 tests passed.
• Local npm run build:unpack: passed.
• git diff --check: passed.
• Remote run 33960193866 passed typecheck, lint, test, Ubuntu and Windows test matrix, Ubuntu and Windows builds, and SonarCloud. macOS is skipped by repository policy.

The PR remains on the correct dev base and is current with dev. I am not approving or merging until the malformed release entry is handled and the PR evidence is completed.

[Zaldaryon]

Approved

The follow-up commit 86e2dd7 closes the prior finding. releasesOf() now filters null and non-object entries before either reader accesses release.tags. The regression covers [null, validRelease] through both game-version option discovery and matching, while valid releases remain available. I found no remaining blocking issue.

Verification

• npm ci: passed with 0 vulnerabilities reported.
• npm run typecheck: passed.
• npm run lint:ci: passed with 0 errors and 15 pre-existing React Hooks warnings.
• npm run format:check: passed.
• npx vitest run tests/domain/mods/installedFilters.test.ts: 28 tests passed.
• npm run test:coverage: 161 files, 2,029 tests passed, 2 skipped; 93.40% statements, 90.20% branches, 92.68% functions, and 94.96% lines.
• npm run build:unpack: passed on Linux with Electron 44.1.1.
• git diff --check: passed.
• Remote CI run 33963603711 passed typecheck, lint, the aggregate test gate, Ubuntu and Windows test matrix legs, Ubuntu and Windows builds, and SonarCloud. macOS is skipped by repository policy.

The PR targets dev, is current with its base, has no unresolved threads, and the reviewed diff contains no private paths, credentials, generated files, or agent traces.