SPARQL-QUERY: queryStr=PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX schema: <http://schema.org/>

construct {
  ?gnd schema:about ?sitelink .
}
where {
  service <http://zbw.eu/beta/sparql/econ_pers/query> {
    ?gnd skos:prefLabel [] ;
         skos:exactMatch ?wd .
    filter(contains(str(?wd), 'wikidata'))
  }
  ?sitelink schema:about ?wd ;
            schema:inLanguage ?language .
  filter (contains(str(?sitelink), 'wikipedia'))
  filter (lang(?wdLabel) = ?language && ?language in ('en', 'de'))
}


java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: java.lang.NullPointerException
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:188)
        at com.bigdata.rdf.sail.webapp.BigdataServlet.submitApiTask(BigdataServlet.java:281)
        at com.bigdata.rdf.sail.webapp.QueryServlet.doSparqlQuery(QueryServlet.java:636)
        at com.bigdata.rdf.sail.webapp.QueryServlet.doGet(QueryServlet.java:278)
        at com.bigdata.rdf.sail.webapp.RESTServlet.doGet(RESTServlet.java:219)
        at com.bigdata.rdf.sail.webapp.MultiTenancyServlet.doGet(MultiTenancyServlet.java:214)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
        at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:808)
        at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:587)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
        at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:577)
        at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
        at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
        at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
        at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
        at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:215)
        at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:110)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
        at org.eclipse.jetty.server.Server.handle(Server.java:497)
        at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:310)
        at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
        at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:540)
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
        at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:188)
        at com.bigdata.rdf.sail.webapp.QueryServlet$SparqlQueryTask.call(QueryServlet.java:834)
        at com.bigdata.rdf.sail.webapp.QueryServlet$SparqlQueryTask.call(QueryServlet.java:653)
        at com.bigdata.rdf.task.ApiTaskForIndexManager.call(ApiTaskForIndexManager.java:68)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        ... 1 more
Caused by: java.lang.NullPointerException
        at com.bigdata.rdf.sparql.ast.optimizers.TypeBasedASTJoinGroupPartitionReorderer.reorderNodes(TypeBasedASTJoinGroupPartitionReorderer.java:84)
        at com.bigdata.rdf.sparql.ast.optimizers.ASTJoinGroupOrderOptimizer.optimizeWithinPartition(ASTJoinGroupOrderOptimizer.java:455)
        at com.bigdata.rdf.sparql.ast.optimizers.ASTJoinGroupOrderOptimizer.optimizeWithinPartitions(ASTJoinGroupOrderOptimizer.java:333)
        at com.bigdata.rdf.sparql.ast.optimizers.ASTJoinGroupOrderOptimizer.optimizeJoinGroup(ASTJoinGroupOrderOptimizer.java:144)
        at com.bigdata.rdf.sparql.ast.optimizers.AbstractJoinGroupOptimizer.optimize(AbstractJoinGroupOptimizer.java:161)
        at com.bigdata.rdf.sparql.ast.optimizers.AbstractJoinGroupOptimizer.optimize(AbstractJoinGroupOptimizer.java:101)
        at com.bigdata.rdf.sparql.ast.optimizers.ASTOptimizerList.optimize(ASTOptimizerList.java:117)
        at com.bigdata.rdf.sparql.ast.eval.AST2BOpUtility.convert(AST2BOpUtility.java:262)
        at com.bigdata.rdf.sparql.ast.eval.ASTEvalHelper.evaluateGraphQuery(ASTEvalHelper.java:525)
        at com.bigdata.rdf.sail.BigdataSailGraphQuery.evaluate(BigdataSailGraphQuery.java:115)
        at com.bigdata.rdf.sail.BigdataSailGraphQuery.evaluate(BigdataSailGraphQuery.java:97)
        at org.openrdf.repository.sail.SailGraphQuery.evaluate(SailGraphQuery.java:113)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$GraphQueryTask.doQuery(BigdataRDFContext.java:1774)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.innerCall(BigdataRDFContext.java:1567)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.call(BigdataRDFContext.java:1532)
        at com.bigdata.rdf.sail.webapp.BigdataRDFContext$AbstractQueryTask.call(BigdataRDFContext.java:704)
        ... 4 more