Error with `resolve-conflicts` #2573

1. Go to "Resolving conflicts" page. E.g. https://github.com/sindresorhus/refined-github/pull/2416/conflicts
2. Feature resolve-conflicts broken with the following errors:

TypeError: "select_dom_default(...)(...) is null"
    format_discussion_titles_init format-discussion-titles.tsx:6
    features_run features.tsx:72
    add features.tsx:123
    onAjaxedPages features.tsx:25
    onAjaxedPagesRaw features.tsx:20
features.tsx:78:16

TypeError: lineHandle.widgets is undefined resolve-conflicts.ts:32:12
    addWidget resolve-conflicts.ts:32
    iterN codemirror.js:5551
    iterN codemirror.js:5666
    iter codemirror.js:6063
    execute/Y</e.exports</Ll.prototype[Vl]</< codemirror.js:9655
    addWidget resolve-conflicts.ts:31