update error message, trigger build failur

Author: wing328

bin/generate-samples.sh

@@ -66,7 +66,7 @@ else
   retcode=${PIPESTATUS[0]}
 fi
 
-if [[ $retcode -ne 0 ]] || grep -q -i "exception" "$tmpfile"; then
+if [[ $retcode -ne 0 ]] || grep -q -i "at org.openapitools" "$tmpfile"; then
   echo "Found exception(s) when running the generator(s) to update the samples."
   exit 1
 fi

modules/openapi-generator/src/main/java/org/openapitools/codegen/OpenAPINormalizer.java

@@ -722,7 +722,7 @@ protected boolean isSelfReference(String name, Schema subSchema) {
      */
     public Schema normalizeSchema(Schema schema, Set<Schema> visitedSchemas) {
         // normalize reference schema
-        if (schema != null && StringUtils.isNotEmpty(schema.get$ref())) {
+        if (StringUtils.isNotEmpty(schema.get$ref())) {
             normalizeReferenceSchema(schema);
         }