Add regression test confirming nullable allOf+$ref fix is dialect-scoped

Confirms, per maintainer feedback on the upstream issue, that the
dynamic evaluation stack walk added for nullable allOf + $ref
compositions has no effect outside dialects that enable the nullable
keyword (currently only OpenAPI 3.0.x) — null is still rejected for
the same schema shape under draft-07.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: tomakehurst

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

@@ -185,6 +185,37 @@ void nullable() {
         assertEquals(1, errors.size());
     }
 
+    @Test
+    void nullableAllOfRefIgnoredOutsideNullableDialect() {
+        String schemaData = """
+                {
+                  "$schema": "http://json-schema.org/draft-07/schema#",
+                  "type": "object",
+                  "required": ["value"],
+                  "properties": {
+                    "value": {
+                      "allOf": [ { "$ref": "#/definitions/Money" } ],
+                      "nullable": true
+                    }
+                  },
+                  "definitions": {
+                    "Money": {
+                      "type": "object",
+                      "required": ["amount"],
+                      "properties": {
+                        "amount": { "type": "integer" }
+                      }
+                    }
+                  }
+                }
+                """;
+        final SchemaRegistry factory = SchemaRegistry.withDefaultDialect(SpecificationVersion.DRAFT_7);
+        final Schema validator = factory.getSchema(schemaData);
+
+        final List<Error> errors = validator.validate("{ \"value\": null }", InputFormat.JSON);
+        assertEquals(1, errors.size());
+    }
+
     @Test
     void integerNonFinite() {
         String schemaData = "{\r\n"