malformed custom theme may break the frontend

setting a custom theme of {} appears to break the frontend, see https://discord.com/channels/1126590789322035230/1163467816284991591/1241353730390098011 and the preceding discussion

we should at the very least ignore such themes, maybe print an error to the console, even better validate them when setting

thanks to 3-for-free / rosey for discovering and investigating the problem

added bugfrontend label

Partially fixed by https://github.com/misskey-dev/misskey/commit/91de35ecdf94bb9ada06eb0c34a597bc50064681 as it now ignores theme code with JSON5 syntax errors

ok, that helps a lot!

it would be also useful if packages/backend/src/server/api/endpoints/admin/update-meta.ts refused to accept a malformed theme (the packages/frontend/src/pages/settings/theme.install.vue does it, for example)

should be fixed by !583 (merged)

closed