Fixes NPE org.apache.lucene.analysis.Analyzer.close(Analyzer.java:152)

java.lang.NullPointerException
>>	at org.apache.lucene.analysis.Analyzer.close(Analyzer.java:152)
>>	at
com.jaeksoft.searchlib.request.SearchField.addQuery(SearchField.java:197)
>>	at
com.jaeksoft.searchlib.request.SearchFieldRequest.newComplexQuery(SearchFieldRequest.java:109)