Fix cloning of parser configuration.

src/main/java/org/json/JSONParserConfiguration.java

@@ -37,6 +37,7 @@ public class JSONParserConfiguration extends ParserConfiguration {
         clone.strictMode = strictMode;
         clone.maxNestingDepth = maxNestingDepth;
         clone.keepStrings = keepStrings;
+        clone.useNativeNulls = useNativeNulls;
         return clone;
     }
 

src/test/java/org/json/junit/JSONParserConfigurationTest.java

@@ -53,6 +53,14 @@ public class JSONParserConfigurationTest {
 
         assertTrue(jsonParserConfiguration.isKeepStrings());
     }
+    
+    @Test
+    public void useNativeNullsIsCloned() {
+        JSONParserConfiguration jsonParserConfiguration = new JSONParserConfiguration()
+                .withUseNativeNulls(true)
+                .withStrictMode(true);
+        assertTrue(jsonParserConfiguration.isUseNativeNulls());
+    }
 
     @Test
     public void verifyDuplicateKeyThenMaxDepth() {