Windows post.jar Can't unambiguously select between fixed arity signatures

[Netz, Steffen]

Hi,

I'm just downloaded solr and playing around.
So far I started the Server and created a core:

bin\solr start
bin\solr create -c files -d example\files\conf

now, I'm trying to post some files:
java -Dauto  -Dc=files -jar example\exampledocs\post.jar 
example\exampledocs\books.csv

and get the following error:
org.apache.solr.common.SolrException: Unable to invoke function processAdd in 
script: update-script.js: Can't unambiguously select between fixed arity 
signatures [(java.lang.String, java.lang.String), (java.lang.String, 
java.io.Reader)] of the method 
org.apache.solr.analysis.TokenizerChain.tokenStream for argument types 
[java.lang.String, null]
                at 
org.apache.solr.update.processor.StatelessScriptUpdateProcessorFactory$ScriptUpdateProcessor.invokeFunction(StatelessScriptUpdateProcessorFactory.java:433)
...
Caused by: java.lang.NoSuchMethodException: Can't unambiguously select between 
fixed arity signatures [(java.lang.String, java.lang.String), 
(java.lang.String, java.io.Reader)] of the method 
org.apache.solr.analysis.TokenizerChain.tokenStream for argument types 
[java.lang.String, null]
                at 
jdk.internal.dynalink.beans.OverloadedMethod.throwAmbiguousMethod(OverloadedMethod.java:225)


Any hint?
Steffen

My Solr: 5.4.1
My Java : java version "1.8.0_71"