title: charAt :error java.lang.NullPointerException
body: <p>I am trying to use talend to check if the 4th character = 4 then I conversion S _ if not we keep the value
  the input file is an Excel file
  who can help me</p>
  
  <pre><code> row1.B.charAt(4) == '4'? StringHandling.CHANGE(StringHandling.LEFT(row1.B,9) ,"_","S"):row1.B    
  </code></pre>
  
  <p>I have this error </p>
  
  <pre><code>[statistics] connected
  Exception in component tMap_1
  java.lang.NullPointerException
      at projectname.test_0_1.test.tFileInputExcel_2Process(test.java:1140)
      at projectname.test_0_1.test.runJobInTOS(test.java:1672)
      at projectname.test_0_1.test.main(test.java:1540)
  </code></pre>