[BUG] ParticipantsRemovedEvent has empty participantsRemoved property

[shuchenku]

Describe the bug
When shareHistoryTime is null for an participant, ParticipantsRemovedEvent converted from ChatEvent payload will have an empty participantsRemoved array.

Exception or Stack Trace
No stack trace but below are the toString()s for ParticipantsRemovedEvent when participantsRemovedJsonString has an null shareHistoryTime versus when it has a valid time.
NULL shareHistoryTime:

{"participantsRemoved":[],
"participantsRemovedJsonString":"[{\"shareHistoryTime\":null,
                                "displayName\":\"Shu2 QA2\",
                                "participantId\":\"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab\",
                                "memberMetaData\":\"null\"}]",
"removedBy":{"communicationIdentifier":{"id":"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab","rawId":"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab"},"displayName":"Shu2 QA2"},
"removedByJsonString":"{\"displayName\":\"Shu2 QA2\",
                        "participantId\":\"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab\",
                        "memberMetaData\":null}",
"removedOn":{"dateTime":{"date":{"day":10,"month":9,"year":2025},"time":{"hour":18,"minute":57,"nano":933451000,"second":38}},
"offset":{"totalSeconds":0}},
"version":"1757530658853",
"groupId":"",
"threadId":"19:acsV2_e814cc46a24f4fb4b0c118167746827d@thread.v2"
}

Valid shareHistoryTime

{"participantsRemoved":[{"communicationIdentifier":{"id":"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab","rawId":"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab"},"displayName":"Shu2 QA2","shareHistoryTime":{"dateTime":{"date":{"day":10,"month":9,"year":2025},"time":{"hour":19,"minute":10,"nano":400000000,"second":1}},"offset":{"totalSeconds":0}}}],
"participantsRemovedJsonString":"[{\"shareHistoryTime\":1757531401400,
                                "displayName\":\"Shu2 QA2\",
                                "participantId\":\"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab\",
                                "memberMetaData\":\"null\"}]",
"removedBy":{"communicationIdentifier":{"id":"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab","rawId":"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab"},"displayName":"Shu2 QA2"},
"removedByJsonString":"{\"displayName\":\"Shu2 QA2\",
                        "participantId\":\"8:acs:ae06a922-4b87-412a-98d5-7e1c5b55edc6_00000025-0c2b-0ce2-1252-573a0d005cab\",
                        "memberMetaData\":null}",
"removedOn":{"dateTime":{"date":{"day":10,"month":9,"year":2025},"time":{"hour":19,"minute":10,"nano":922730500,"second":12}},
"offset":{"totalSeconds":0}},
"version":"1757531412859",
"groupId":"",
"threadId":"19:acsV2_444db53cebd24019a5e81967afaec64a@thread.v2"}

To Reproduce
Prereq: Have Users A, B, C, etc. as valid ACS users; all users subscribing to ACS realtime events on Android clients.
Steps to reproduce the behavior:

1. As User A, use the 'chat/threads' ACS endpoint to create a group chat that contains users A, B, and C.
2. As User B, call 'chat/threads/{threadId}/participants/:remove' with their ACS id to leave the chat.
3. On User A's device, observe the PARTICIPANTS_REMOVED event: participantsRemovedJsonString contains removed participant info for User B
4. When converted the event data to an ParticipantsRemovedEvent instance, participantsRemoved array is empty.

Code Snippet
ChatAsyncClient chatAsyncClient = MessagesClient.getChatAsyncClient();

    Log.i(TAG, "Starting real time notification for participants removed");
    chatAsyncClient.addEventHandler(ChatEventType.PARTICIPANTS_REMOVED,
            (ChatEvent payload) -> handler.post(() -> {
                ParticipantsRemovedEvent removeParticipantsEvent = (ParticipantsRemovedEvent) payload;

                List<ChatParticipant> participantsRemoved = removeParticipantsEvent.getParticipantsRemoved();
                if (participantsRemoved != null && !participantsRemoved.isEmpty()) {
                    try {
                        ChatParticipant chatParticipant = participantsRemoved.get(0);
                        CommunicationIdentifier identifier = chatParticipant.getCommunicationIdentifier();
                        String participantAcsId = ((CommunicationUserIdentifier) identifier).getId();

                        ChatParticipant removedBy = removeParticipantsEvent.getRemovedBy();
                        String removedByAcsId = ((CommunicationUserIdentifier) removedBy
                                .getCommunicationIdentifier()).getId();

                        HashMap<String, String> participantPayload = new HashMap<>();

                        participantPayload.put("eventType", ChatEventType.PARTICIPANTS_REMOVED.toString());
                        participantPayload.put("threadId", removeParticipantsEvent.getChatThreadId());
                        participantPayload.put("removedOn", removeParticipantsEvent.getRemovedOn().toString());
                        participantPayload.put("actionByAcsId", removedByAcsId);
                        participantPayload.put("participantsRemoved", new Gson().toJson(participantsRemoved));
                        event.success(participantPayload);
                    } catch (Exception e) {
                        Log.e(TAG, "Error handling participants removed event: " + e.getMessage());
                    }
                } else {
                    Log.e(TAG, "Participants removed list is null or empty");
                }
            })
    );

Expected behavior
The ParticipantsRemovedEvent converted from the ChatEvent payload should have the removed participant data in participantsRemoved even when shareHistoryTime is empty.

Screenshots
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Setup (please complete the following information):

• OS: Android 16
• IDE : VSCode?
• azure-communication-chat:2.0.2/azure-communication-common:1.0.2

Additional context
Add any other context about the problem here.

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