schema name null fix

This is to fix the issue mentioned here
springdoc/springdoc-openapi#1266

Author: kenzhang-mark43

modules/swagger-core/src/main/java/io/swagger/v3/core/jackson/ModelResolver.java

@@ -867,7 +867,7 @@ public Schema resolve(AnnotatedType annotatedType, ModelConverterContext context
             StringUtils.isNotBlank(model.getName()))
         {
             if (context.getDefinedModels().containsKey(model.getName())) {
-                model = new Schema().$ref(constructRef(model.getName()));
+                model = new Schema().name(model.getName()).$ref(constructRef(model.getName()));
             }
         } else if (model != null && model.get$ref() != null) {
             model = new Schema().$ref(StringUtils.isNotEmpty(model.get$ref()) ? model.get$ref() : model.getName());