@smui/common - "Type 'CustomEvent<T | undefined>' is not assignable to type 'CustomEvent<T>'" error when strictNullChecks is enabled in tsconfig

[DetachHead]

Describe the bug
the following errors occur when running svelte-check with the strictNullChecks compiler option enabled in tsconfig.json:

c:\project\node_modules\@smui\common\src\internal\dispatch.ts:10:11
Error: Type 'CustomEvent<T | undefined>' is not assignable to type 'CustomEvent<T>'.
  Type 'T | undefined' is not assignable to type 'T'.
    'T | undefined' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'unknown'.
      Type 'undefined' is not assignable to type 'T'.
        'undefined' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'unknown'.
  if (typeof Event !== 'undefined' && element) {
    const event: CustomEvent<T> = new CustomEvent(eventType, {
      ...eventInit,


c:\project\node_modules\@smui\common\src\internal\dispatch.ts:16:13
Error: Type 'CustomEvent<T | undefined>' is not assignable to type 'CustomEvent<T>'.
    if (duplicateEventForMDC && eventType.startsWith('SMUI')) {
      const duplicateEvent: CustomEvent<T> = new CustomEvent(
        eventType.replace(/^SMUI/g, () => 'MDC'),

To Reproduce
Steps to reproduce the behavior:

1. enable strictNullChecks in tsconfig.json:

   {
       "compilerOptions": {
           "strictNullChecks": true,
           "skipLibCheck": false
       }
   }

2. run svelte-check

Expected behavior
no error

[DetachHead]

after some investigating i noticed that this is caused by typesVersions in the @smui/common package incorrectly pointing to the source code. see #532