reorder xssf code

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1906981 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSheet.java

             throw new POIXMLException(e);
         }
 
-        initRows(worksheet);
         columnHelper = new ColumnHelper(worksheet);
+        initRows(worksheet);
         // Look for bits we're interested in
         for(RelationPart rp : getRelationParts()){
             POIXMLDocumentPart p = rp.getDocumentPart();