making snapshot listener nullable to preserve original firestore API behavior

Author: Horácio Comé

fireflow/src/main/java/io/github/horaciocome1/fireflow/Extensions.kt

@@ -32,7 +32,7 @@ import kotlin.coroutines.CoroutineContext
 inline fun <reified T> Query.asFlow(
     coroutineContext: CoroutineContext = Dispatchers.IO,
 ): Flow<MutableList<T>> = snapshotAsFlow(coroutineContext).map {
-    it.toObjects(T::class.java)
+    it?.toObjects(T::class.java) ?: mutableListOf()
 }
 
 /**
@@ -43,5 +43,5 @@ inline fun <reified T> Query.asFlow(
 inline fun <reified T> DocumentReference.asFlow(
     coroutineContext: CoroutineContext = Dispatchers.IO,
 ): Flow<T?> = snapshotAsFlow(coroutineContext).map {
-    it.toObject(T::class.java)
+    it?.toObject(T::class.java)
 }

fireflow/src/main/java/io/github/horaciocome1/fireflow/Snapshot.kt

@@ -38,10 +38,10 @@ import kotlin.coroutines.CoroutineContext
 @ExperimentalCoroutinesApi
 fun DocumentReference.snapshotAsFlow(
     coroutineContext: CoroutineContext = Dispatchers.IO,
-): Flow<DocumentSnapshot> = callbackFlow {
+): Flow<DocumentSnapshot?> = callbackFlow {
     try {
         val listener = EventListener<DocumentSnapshot> { snapshot, error ->
-            if (error != null || snapshot == null) {
+            if (error != null) {
                 close(error)
                 return@EventListener
             }
@@ -63,10 +63,10 @@ fun DocumentReference.snapshotAsFlow(
 @ExperimentalCoroutinesApi
 fun Query.snapshotAsFlow(
     coroutineContext: CoroutineContext = Dispatchers.IO,
-): Flow<QuerySnapshot> = callbackFlow {
+): Flow<QuerySnapshot?> = callbackFlow {
     try {
         val listener = EventListener<QuerySnapshot> { snapshot, error ->
-            if (error != null || snapshot == null) {
+            if (error != null) {
                 close(error)
                 return@EventListener
             }