Exception message for invalid token is unclear

[romani]

$ cat Test.java 
public class Test {
   private Optional<String> field1;
}

$ cat config.xml 
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
          "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
    <module name="TreeWalker">
        <module name="IllegalType">
            <property name="illegalClassNames" value="java.util.Optional" />
            <property name="tokens" value="VARIABLE_DEF" />
            <property name="memberModifiers" value=""/>
        </module>
   </module>
</module>

$ java -jar checkstyle-8.36.2-all.jar -c config.xml Test.java
com.puppycrawl.tools.checkstyle.api.CheckstyleException: cannot initialize module TreeWalker - cannot initialize module IllegalType - Cannot set property 'memberModifiers' to ''
	at com.puppycrawl.tools.checkstyle.Checker.setupChild(Checker.java:482)
	at com.puppycrawl.tools.checkstyle.api.AutomaticBean.configure(AutomaticBean.java:201)
	at com.puppycrawl.tools.checkstyle.Main.runCheckstyle(Main.java:404)
	at com.puppycrawl.tools.checkstyle.Main.runCli(Main.java:331)
	at com.puppycrawl.tools.checkstyle.Main.execute(Main.java:190)
	at com.puppycrawl.tools.checkstyle.Main.main(Main.java:125)
Caused by: com.puppycrawl.tools.checkstyle.api.CheckstyleException: cannot initialize module IllegalType - Cannot set property 'memberModifiers' to ''
	at com.puppycrawl.tools.checkstyle.TreeWalker.setupChild(TreeWalker.java:125)
	at com.puppycrawl.tools.checkstyle.api.AutomaticBean.configure(AutomaticBean.java:201)
	at com.puppycrawl.tools.checkstyle.Checker.setupChild(Checker.java:477)
	... 5 more
Caused by: com.puppycrawl.tools.checkstyle.api.CheckstyleException: Cannot set property 'memberModifiers' to ''
	at com.puppycrawl.tools.checkstyle.api.AutomaticBean.tryCopyProperty(AutomaticBean.java:241)
	at com.puppycrawl.tools.checkstyle.api.AutomaticBean.configure(AutomaticBean.java:194)
	at com.puppycrawl.tools.checkstyle.TreeWalker.setupChild(TreeWalker.java:120)
	... 7 more
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.commons.beanutils.PropertyUtilsBean.invokeMethod(PropertyUtilsBean.java:2128)
	at org.apache.commons.beanutils.PropertyUtilsBean.setSimpleProperty(PropertyUtilsBean.java:2109)
	at org.apache.commons.beanutils.BeanUtilsBean.copyProperty(BeanUtilsBean.java:437)
	at com.puppycrawl.tools.checkstyle.api.AutomaticBean.tryCopyProperty(AutomaticBean.java:231)
	... 9 more
Caused by: java.lang.IllegalArgumentException: given name 
	at com.puppycrawl.tools.checkstyle.utils.TokenUtil.getTokenId(TokenUtil.java:174)
	at com.puppycrawl.tools.checkstyle.checks.coding.IllegalTypeCheck.setMemberModifiers(IllegalTypeCheck.java:828)
	... 17 more
Checkstyle ends with 1 errors.

one more case - checkstyle/sonar-checkstyle#338 (comment)

Expected:
java.lang.IllegalArgumentException: unknown TokenTypes value ''