Bug: Angular 12 full strict mode optional key pipe error

[eggp]

Current behavior

In Angular 12 full strict mode, I get an error with a conditional key.
Angular 12 tsconfig: https://github.com/eggp/translocoNG12StrictPipeError/blob/master/apps/test/tsconfig.json#L16
Error:

Error: apps/test/src/app/app.component.html:1:8 - error TS2345: Argument of type 'string | undefined' is not assignable to parameter of type 'string | null'.
  Type 'undefined' is not assignable to type 'string | null'.

1 <div>{{options1?.some | transloco}}</div>
         ~~~~~~~~~~~~~~

  apps/test/src/app/app.component.ts:6:16
    6   templateUrl: './app.component.html',
                     ~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component AppComponent.

Expected behavior

Accept undefined value as pipe key value.
Please add undefined to key type def. => https://github.com/ngneat/transloco/blob/faa58a5a0b73595173e3b5a640e4157d8ec50428/projects/ngneat/transloco/src/lib/transloco.pipe.ts#L35
Correct:

transform(key: string | null | undefined, params?: HashMap | undefined, inlineLang?: string | undefined): string {

Minimal reproduction of the problem with instructions

https://github.com/eggp/translocoNG12StrictPipeError

Environment

- Transloco version: 2.22.0
- Angular version: 12.X.X

Browser:

• Chrome (desktop) version XX
• Chrome (Android) version XX
• Chrome (iOS) version XX
• Firefox version XX
• Safari (desktop) version XX
• Safari (iOS) version XX
• IE version XX
• Edge version XX