Program: 126172
Project: 126172
Buggy source:
@Override public boolean preProcessStart(){
  previewButton.setText(Messages.getString("String_Node_Str"));
  clearPreview();
  String filePath=getConnection().getFilePath();
  FileExcelConnection originalValueConnection=null;
  if (isContextMode()) {
    boolean found=false;
    ContextType contextType=ConnectionContextHelper.getContextTypeForContextMode(getShell(),getConnection(),getConnection().getContextName(),false);
    if (contextType != null) {
      if (getContextModeManager() != null) {
        getContextModeManager().setSelectedContextType(contextType);
        filePath=getContextModeManager().getOriginalValue(getConnection().getFilePath());
        filePath=TalendQuoteUtils.removeQuotes(filePath);
        found=true;
      }
      setConnectionProperties();
      originalValueConnection=(FileExcelConnection)FileConnectionContextUtils.cloneOriginalValueConnection(getConnection(),contextType);
    }
    if (!found) {
      filePath=null;
    }
  }
  if (filePath == null || filePath.equals("String_Node_Str")) {
    previewInformationLabel.setText("String_Node_Str" + Messages.getString("String_Node_Str"));
    return false;
  }
  if (!checkFieldsValue()) {
    previewInformationLabel.setText("String_Node_Str" + Messages.getString("String_Node_Str"));
    return false;
  }
  previewInformationLabel.setText("String_Node_Str" + Messages.getString("String_Node_Str"));
  firstRowIsCatption=firstRowIsCaptionCheckbox.getSelection();
  if (originalValueConnection == null) {
    originalValueConnection=getConnection();
  }
  processDescription=getProcessDescription(originalValueConnection);
  return true;
}

Fixed version (ground truth):
@Override public boolean preProcessStart(){
  previewButton.setText(Messages.getString("String_Node_Str"));
  clearPreview();
  String filePath=getConnection().getFilePath();
  FileExcelConnection originalValueConnection=null;
  if (isContextMode()) {
    boolean found=false;
    ContextType contextType=ConnectionContextHelper.getContextTypeForContextMode(getShell(),getConnection(),getConnection().getContextName(),false);
    if (contextType != null) {
      if (getContextModeManager() != null) {
        getContextModeManager().setSelectedContextType(contextType);
        filePath=getContextModeManager().getOriginalValue(getConnection().getFilePath());
        filePath=TalendQuoteUtils.removeQuotes(filePath);
        found=true;
      }
      setConnectionProperties();
      originalValueConnection=(FileExcelConnection)FileConnectionContextUtils.cloneOriginalValueConnection(getConnection(),contextType);
    }
    if (!found) {
      filePath=null;
    }
  }
  if (filePath == null || filePath.equals("String_Node_Str")) {
    previewInformationLabel.setText("String_Node_Str" + Messages.getString("String_Node_Str"));
    return false;
  }
  if (!checkFieldsValue()) {
    previewInformationLabel.setText("String_Node_Str" + Messages.getString("String_Node_Str"));
    return false;
  }
  previewInformationLabel.setText("String_Node_Str" + Messages.getString("String_Node_Str"));
  firstRowIsCatption=firstRowIsCaptionCheckbox.getSelection();
  if (originalValueConnection == null) {
    originalValueConnection=getConnection();
  }
  processDescription=getProcessDescription(originalValueConnection);
  updateStatus(IStatus.ERROR,null);
  return true;
}