Android get paywalls bug

[Another1dd]

E/flutter ( 8702): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: type 'Null' is not a subtype of type 'String'
E/flutter ( 8702): #0 new AdaptyProduct.fromMap (package:adapty_flutter/models/adapty_product.dart:98:24)
E/flutter ( 8702): #1 new AdaptyPaywall.fromMap. (package:adapty_flutter/models/adapty_paywall.dart:43:138)
E/flutter ( 8702): #2 MappedListIterable.elementAt (dart:_internal/iterable.dart:411:31)
E/flutter ( 8702): #3 ListIterator.moveNext (dart:_internal/iterable.dart:340:26)
E/flutter ( 8702): #4 new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:188:27)
E/flutter ( 8702): #5 new _GrowableList.of (dart:core-patch/growable_array.dart:150:28)
E/flutter ( 8702): #6 new List.of (dart:core-patch/array_patch.dart:50:28)
E/flutter ( 8702): #7 ListIterable.toList (dart:_internal/iterable.dart:211:44)
E/flutter ( 8702): #8 new AdaptyPaywall.fromMap (package:adapty_flutter/models/adapty_paywall.dart:43:153)
E/flutter ( 8702): #9 new GetPaywallsResult.fromMap. (package:adapty_flutter/results/get_paywalls_result.dart:10:105)
E/flutter ( 8702): #10 MappedListIterable.elementAt (dart:_internal/iterable.dart:411:31)
E/flutter ( 8702): #11 ListIterator.moveNext (dart:_internal/iterable.dart:340:26)
E/flutter ( 8702): #12 new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:188:27)
E/flutter ( 8702): #13 new _GrowableList.of (dart:core-patch/growable_array.dart:150:28)
E/flutter ( 8702): #14 new List.of (dart:core-patch/array_patch.dart:50:28)
E/flutter ( 8702): #15 ListIterable.toList (dart:_internal/iterable.dart:211:44)
E/flutter ( 8702): #16 new GetPaywallsResult.fromMap (package:adapty_flutter/results/get_paywalls_result.dart:10:117)
E/flutter ( 8702): #17 Adapty.getPaywalls (package:adapty_flutter/adapty_flutter.dart:62:30)

[AKyashkin]

Fixed in 1.0.0-nullsafety.0 pre-release.
https://github.com/adaptyteam/AdaptySDK-Flutter/tree/1.0.0-nullsafety.0