Steps to replicate the issue (include links if applicable):

• Utilize an API request, either through the use of the API test page or a JavaScript query, with the specified parameters to retrieve the desired result. For example: https://pl.wikipedia.org/wiki/Specjalna:Środowisko_testowe_API#action=parse&format=json&page=Dyskusja_wikipedysty%3AKrzysiek_123456789%2FArchiwum&prop=sections&formatversion=2

What happens?:
It may happen that when making API requests for certain sections, the API does not return an index for those sections.

Upon examining the screenshot of the API request, it appears that there are two instances where the index value is missing for a section. These instances occur between the sections with indexes 496 and 497, as well as between the sections with indexes 505 and 506. Regardless of the cause, it is evident that there are two instances where the index value is not present for certain sections in the API request.

What should have happened instead?
It is expected that all index values for the relevant sections would be returned in the API response. It would be preferable for all index values to be returned as expected, in order to facilitate accurate and complete processing of the data.

Software version (skip for WMF-hosted wikis like Wikipedia):
polish wikipedia