[BUG] GET /group/participants/{instance} returns 500 'Cannot convert undefined or null to object' on v2.4.0 #2739

Description

The GET /group/participants/{instance}?groupJid={jid} endpoint returns a 500 Internal Server Error with "Cannot convert undefined or null to object" on Evolution API v2.4.0 (Baileys 7.0.0-rc14), even when:

• The instance is connected (connectionState returns {"state": "open"})
• The group exists and has 81 participants (verified via direct DB sync)
• The same groupJid works with other group endpoints (metadata sync works fine)

Steps to reproduce

1. Connect an instance (state: open)
2. Have a WhatsApp group with participants (in our case: 81 participants, all @lid JIDs)
3. Call GET /group/participants/{instance}?groupJid=120363400304389821@g.us

Expected behavior

Return the list of participants with their roles.

Actual behavior

{
  "status": 500,
  "error": "Internal Server Error",
  "response": {
    "message": "Cannot convert undefined or null to object"
  }
}

Same error on GET /group/findGroupInfos/{instance}?groupJid=... and GET /group/fetchAllGroups/{instance}.

Environment

• Evolution API version: 2.4.0
• Baileys version: 7.0.0-rc14
• Docker deployment
• Instance state: open (verified)
• Group has 81 participants, all @lid JIDs (WhatsApp LID privacy feature)

Additional context

The group participant sync works via a separate internal path (cron job), so the group data IS accessible. The on-demand REST endpoint specifically fails. This may be related to how Baileys 7.0.0-rc14 handles LID-only group metadata (no PN JIDs available for participants).

Not sure if this is a Baileys upstream issue or an Evolution API mapping problem, but the error Cannot convert undefined or null to object suggests the code is trying to process participant data that came back as null/undefined from Baileys.