If you are facing this issue in kotlin

**if your code is like this**

data class ChatMessage(
   var messageText: String?,
   var messageUser: String?,
   var messageTime: Long?)

Then First Add Secondary constructor

data class ChatMessage(
    var messageText: String = "",
    var messageUser: String = "",
    var messageTime: Long = 0L
) {
    // Secondary constructor
    constructor() : this("", "", 0L)
}

Second main thing is add @Kepp

import androidx.annotation.Keep

@Keep
data class ChatMessage(
    var messageText: String = "",
    var messageUser: String = "",
    var messageTime: Long = 0L
) {
    // Secondary constructor
    constructor() : this("", "", 0L)
}

By adding @keep

1. The entire ChatMessage class and its fields will be preserved during the build process.

2. It's especially important for classes used in Firebase Realtime Database, GSON, or other frameworks relying on reflection.