Small unimportant fix to example code.

git-svn-id: https://svn.apache.org/repos/asf/jakarta/poi/branches/REL_2_BRANCH@353359 13f79535-47bb-0310-9956-ffa450edef68

src/examples/src/org/apache/poi/hssf/usermodel/examples/ReadWriteWorkbook.java

@@ -80,6 +80,8 @@ public class ReadWriteWorkbook
         HSSFWorkbook wb = new HSSFWorkbook(fs);
         HSSFSheet sheet = wb.getSheetAt(0);
         HSSFRow row = sheet.getRow(2);
+        if (row == null)
+            row = sheet.createRow(2);
         HSSFCell cell = row.getCell((short)3);
         if (cell == null)
             cell = row.createCell((short)3);