Guard in GithubProvider custom channel breaks case of no prerelease versions

[blakebyrnes]

Whoops, seems there was an error in some code I suggested:

packages/electron-updater/src/providers/GitHubProvider.ts:76:63 - error TS2345: Argument of type 'string | number | null' is not assignable to parameter of type 'string'.
  Type 'null' is not assignable to type 'string'.

76           const isCustomChannel = !['alpha', 'beta'].includes(hrefChannel)

Since we don't care about number/null when comparing against alpha/beta, let's just wrap hrefChannel to be String(hrefChannel)

Originally posted by @mmaietta in #6505 (comment)

[blakebyrnes]

This ticket has a strange format. Sorry for that. I was trying to reference where this originated. There's an issue if you use the allowPrerelease feature of the GithubProvider that causes it to fail to find any github releases if the current version is not a prerelease.

electron-builder/packages/electron-updater/src/providers/GitHubProvider.ts

Line 60 in 8b43098

const currentChannel = this.updater?.channel || String(semver.prerelease(this.updater.currentVersion)?.[0]) || null

The string wrap added above causes the || null to never occur. It evaluates to the string 'undefined'. The same string wrap was not added to the comparison a few lines below, so it fails to properly match the condition where there's no currentChannel.

electron-builder/packages/electron-updater/src/providers/GitHubProvider.ts

Line 71 in 8b43098

const hrefChannel = semver.prerelease(hrefTag)?.[0] || null

Solution seems to be to just wrap the second option.

[mmaietta]

Can you please open a PR with the fix? 🙂