fix(helpdesk): fix reportSunburstTicketByCategories chart

[MyvTsv]

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !42269
• The Distribution of tickets per category and child categories chart did not display subcategories if at least two ancestors were assigned to no tickets.

Screenshots (if appropriate):

Before fix:

After fix: