message_event library Null safety

Classes

LoadChannelMessageEvent
LoadHistoryMessageEvent
LoadTopicMessageEvent
LoadUnreadAgentMessagesEvent
LoadUnreadMessagesEvent
LoadUnreadVisitorMessagesEvent
MessageAnswerEvent
MessageEvent
QueryAnswerEvent
QueryCategoryEvent
RateAnswerEvent
ReceiveMessageEvent
SendMessageRestEvent
UploadImageEvent
UploadVideoEvent