Unable to use backport

I'm trying to backport https://github.com/mapbox/mapbox-gl-native/pull/12128 to release-chai, but not able to get it working. Probably doing something very trivial wrong here. These are the commands I tried:

backport ddc4b03c3416f1442a1e177ff5f7de7bf2a8e707 release-chai

{ Error: 'number' cannot be null
at values.forEach (/usr/local/lib/node_modules/@mapbox/github-release-tools/node_modules/@octokit/rest/lib/plugins/endpoint-methods/validate.js:75:15)
at Array.forEach (native)
at Object.keys.forEach.parameterName (/usr/local/lib/node_modules/@mapbox/github-release-tools/node_modules/@octokit/rest/lib/plugins/endpoint-methods/validate.js:53:12)
at Array.forEach (native)
at validate (/usr/local/lib/node_modules/@mapbox/github-release-tools/node_modules/@octokit/rest/lib/plugins/endpoint-methods/validate.js:31:31)
at
at process._tickCallback (internal/process/next_tick.js:169:7)
at Function.Module.runMain (module.js:607:11)
at startup (bootstrap_node.js:158:16)
at bootstrap_node.js:575:3
name: 'HttpError',
code: 400,
status: 'Bad Request',
headers: undefined }

backport https://github.com/mapbox/mapbox-gl-native/pull/12128 release-chai

{ Error: no reference found for shorthand 'release-chai' errno: -3, errorFunction: 'Reference.dwim' }

backport #12128 release-chai

Not enough non-option arguments: got 0, need at least 2

issue に記載されている 3 つの backport コマンドを再現し、その後、コマンドの引数処理と、number エラーに関して参照されている @octokit/rest validation.js の位置を調査します。pull request 12128 から release-chai への意図した backport が報告されたエラーなしで実行されれば完了です。