NPE during JSON schema walk with validation

[chrishodgins]

We ran into this while migrating to 1.5.5. A JSON schema walk returned an NPE rather than returning validation messages while validating a YAML document that did not have the corresponding properties. Below is the smallest recreate I've found that still fails with an NPE. I've replaced the YAML nodes with an instance of the MissingNode below to simulate the missing object properties.

import com.fasterxml.jackson.databind.node.MissingNode;
import com.networknt.schema.JsonSchema;
import com.networknt.schema.JsonSchemaFactory;
import com.networknt.schema.SpecVersion;

public class SchemaTest {

    public static void main(String[] args) {
        String schemaContents = """
            {
                "type": "object",
                "properties": {
                    "field": {
                    "anyOf": [
                        {
                        "type": "string"
                        }
                    ]
                    }
                }
            }
            """;

        JsonSchemaFactory factory = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V7);
        JsonSchema schema = factory.getSchema(schemaContents);
        schema.walk(MissingNode.getInstance(), true).getValidationMessages();
    }
}

Stack trace:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "com.fasterxml.jackson.databind.JsonNode.getNodeType()" because "node" is null
        at com.networknt.schema.TypeFactory.getValueNodeType(TypeFactory.java:78)
        at com.networknt.schema.utils.JsonNodeUtil.equalsToSchemaType(JsonNodeUtil.java:70)
        at com.networknt.schema.TypeValidator.equalsToSchemaType(TypeValidator.java:50)
        at com.networknt.schema.AnyOfValidator.validate(AnyOfValidator.java:84)
        at com.networknt.schema.AnyOfValidator.walk(AnyOfValidator.java:166)
        at com.networknt.schema.JsonSchema.walk(JsonSchema.java:1278)
        at com.networknt.schema.PropertiesValidator.walkSchema(PropertiesValidator.java:197)
        at com.networknt.schema.PropertiesValidator.validate(PropertiesValidator.java:109)
        at com.networknt.schema.PropertiesValidator.walk(PropertiesValidator.java:133)
        at com.networknt.schema.JsonSchema.walk(JsonSchema.java:1278)
        at com.networknt.schema.JsonSchema.walkAtNodeInternal(JsonSchema.java:1247)
        at com.networknt.schema.JsonSchema.walk(JsonSchema.java:1082)
        at com.networknt.schema.JsonSchema.walk(JsonSchema.java:1162)
       ...

[chrishodgins]

Many thanks for fixing this so quickly!