Merge branch 'master' into develop

moor/lib/src/runtime/data_class.dart

@@ -86,7 +86,11 @@ class _DefaultValueSerializer extends ValueSerializer {
   @override
   T fromJson<T>(json) {
     if (T == DateTime) {
-      return DateTime.fromMillisecondsSinceEpoch(json as int) as T;
+      if (json == null) {
+        return null;
+      } else {
+        return DateTime.fromMillisecondsSinceEpoch(json as int) as T;
+      }
     }
 
     return json as T;

moor/test/serialization_test.dart

@@ -54,6 +54,12 @@ class CustomSerializer extends ValueSerializer {
 }
 
 void main() {
+  test('default serializer', () {
+    final serializer = const ValueSerializer.defaults();
+    expect(serializer.toJson<DateTime>(null), null);
+    expect(serializer.fromJson<DateTime>(null), null);
+  });
+
   group('serialization', () {
     test('with defaults', () {
       expect(someTodoEntry.toJson(), equals(regularSerialized));

moor/test/transactions_test.dart

@@ -19,6 +19,7 @@ void main() {
     expect(() async {
       await db.transaction((t) {
         t.select(db.users).watch();
+        return Future.value(null); // analysis warning in travis otherwise
       });
     }, throwsStateError);