ruby on rails - Reindexing fails after upgrading solr -

i used sunspot_solr , sunspot_rails gem integrates solr 4 following link..

source

now, when try reindex existing documents, status 500, internal server error..

i removed solr directory , after bundle install, , gave following commands

rails generate sunspot_rails:install rake sunspot:solr:run 

where going wrong? :/

when tried reindex in rails console, got following error...

when tried reindexing in rails console, got following error.. 

rsolr::error::http: rsolr::error::http - 500 internal server error error: {'responseheader'=>{'status'=>500,'qtime'=>10},'error'=>{'trace'=>'java.lang.nullpointerexception @ org.apache.solr.update.documentbuilder.todocument(documentbuilder.java:232) @ org.apache.solr.update.addupdatecommand.getlucenedocument(addupdatecommand.java:73) @ org.apache.solr.update.directupdatehandler2.adddoc(directupdatehandler2.java:204) @ org.apache.solr.update.processor.runupdateprocessor.processadd(runupdateprocessorfactory.java:69) @ org.apache.solr.update.processor.updaterequestprocessor.processadd(updaterequestprocessor.java:51) @ org.apache.solr.update.processor.distributedupdateprocessor.dolocaladd(distributedupdateprocessor.java:451) @ org.apache.solr.update.processor.distributedupdateprocessor.versionadd(distributedupdateprocessor.java:587) @ org.apache.solr.update.processor.distributedupdateprocessor.processadd(distributedupdateprocessor.java:346) @ org.apache.solr.update.processor.logupdateprocessor.processadd(logupdateprocessorfactory.java:100) @ org.apache.solr.handler.loader.xmlloader.processupdate(xmlloader.java:246)

the stopwords causing problems... had changes in schema.xml(as used ngrams in project) , fixed stopwards problem.. working fine :)