Merge pull request #1249 from RafaRuiz/fix/initial_nullables

Initial nullables

@@ -247,7 +247,7 @@ class RxBool extends Rx<bool> {
 }
 }
 
 
 class RxnBool extends Rx<bool?> {
 class RxnBool extends Rx<bool?> {
-  RxnBool(bool initial) : super(initial);
+  RxnBool(bool? initial) : super(initial);
   @override
   @override
   String toString() {
   String toString() {
     return "$value";
     return "$value";

@@ -578,7 +578,7 @@ class RxNum extends Rx<num> {
 }
 }
 
 
 class RxnNum extends Rx<num?> {
 class RxnNum extends Rx<num?> {
-  RxnNum(num initial) : super(initial);
+  RxnNum(num? initial) : super(initial);
 
 
   num? operator +(num other) {
   num? operator +(num other) {
     if (value != null) {
     if (value != null) {