In Java21, the ConstPool API throws NPE for MethodParameters attributes without parameter names

[wuwen5]

public void testJava21() throws NotFoundException {
        CtClass ctClass = sloader.get("sun.net.httpserver.ServerImpl$ReqRspTimeoutTask");
        ctClass.getClassFile().compact();
}

java.lang.NullPointerException: Cannot read field "string" because "utf" is null
	at javassist.bytecode.ConstPool.getUtf8Info(ConstPool.java:675)
	at javassist.bytecode.MethodParametersAttribute.copy(MethodParametersAttribute.java:90)
	at javassist.bytecode.AttributeInfo.copyAll(AttributeInfo.java:249)
	at javassist.bytecode.MethodInfo.compact(MethodInfo.java:157)
	at javassist.bytecode.ClassFile.compact(ClassFile.java:242)
	at javassist.JvstTest4.testJdk21(JvstTest4.java:1008)

An error occurred while processing MethodParametersAttribute

In the construction method of the inner class, there are MethodParameters attributes without parameter names.

MethodParameters:
      Name                           Flags
      <no name>                      final mandated

openjdk/jdk#13167 (comment)

And just to double-check, the JVMS does allow the parameter name information to be missing even if the access flags are defined: https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.7.24

name_index

The value of the name_index item must either be zero or a valid index into the constant_pool table.

If the value of the name_index item is zero, then this parameters element indicates a formal parameter with no name.

If the value of the name_index item is nonzero, the constant_pool entry at that index must be a CONSTANT_Utf8_info structure representing a valid unqualified name denoting a formal parameter ([§4.2.2](https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.2.2)).