Added handling for null class objects

strategy/to_json/from_serializable.ts

@@ -11,6 +11,10 @@ export function fromSerializable(): ToJSONStrategy {
     if (Array.isArray(value)) {
       return value.map((item) => item.tsSerialize());
     }
+    else if (value === null) {
+      // Objects can be null, return them without further serialization.
+      return value;
+    }
     return value.tsSerialize();
   };
 }

strategy/to_json/from_serializable_test.ts

@@ -45,6 +45,32 @@ test({
   },
 });
 
+test({
+  name: "fromSerializable - arrays of nested objects with nested object set to null",
+  fn() {
+    class Test1 extends Serializable {
+      @SerializeProperty("nested_property")
+      serializeMe = 999;
+    }
+    class Test2 extends Serializable {
+      @FromSerializable("outer_property")
+      nested: Test1[] = [new Test1()];
+    }
+
+    class Test3 extends Serializable {
+      @FromSerializable("outer_outer_property")
+      nested2: Test2[] = [new Test2()];
+    }
+    const testObj = new Test3();
+    testObj.nested = null;
+
+    assertEquals(
+      testObj.toJSON(),
+      `{"outer_outer_property":null}]}`,
+    );
+  },
+});
+
 test({
   name: "fromSerializable - single serializable objects",
   fn() {
@@ -69,3 +95,31 @@ test({
     );
   },
 });
+
+
+test({
+  name: "fromSerializable - single serializable objects with a nested object set to null",
+  fn() {
+    class Test1 extends Serializable {
+      @SerializeProperty("nested_property")
+      serializeMe = 999;
+    }
+    class Test2 extends Serializable {
+      @FromSerializable("outer_property")
+      nested: Test1 = new Test1();
+    }
+
+    class Test3 extends Serializable {
+      @FromSerializable("outer_outer_property")
+      nested2: Test2 = new Test2();
+    }
+
+    const testObj = new Test3();
+    testObj.nested2 = null;
+
+    assertEquals(
+      testObj.toJSON(),
+      `{"outer_outer_property":null}`,
+    );
+  },
+});