#604 add disabled test case to reproduce the NPE

Author: stevehu

src/test/java/com/networknt/schema/Issue604Test.java

@@ -0,0 +1,23 @@
+package com.networknt.schema;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+public class Issue604Test {
+    @Test
+    @Disabled("This test is disabled until the issue is fixed")
+    public void failure() {
+        SchemaValidatorsConfig config = new SchemaValidatorsConfig();
+        config.setApplyDefaultsStrategy(new ApplyDefaultsStrategy(true, false, false));
+        JsonSchemaFactory factory = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V7);
+        JsonSchema schema = factory.getSchema("{ \"type\": \"object\", \"properties\": { \"foo\": { \"type\": \"object\", \"properties\": { \"bar\": { \"type\": \"boolean\", \"default\": false } } } } }", config);
+        ObjectMapper objectMapper = new ObjectMapper();
+        assertDoesNotThrow(() -> {
+            schema.walk(objectMapper.readTree("{}"), false);
+        });
+    }
+
+}