The error message "failed: private method 'split' called for nil:Nilclass" get displayed while performing custom import. How it can be solved?

 The error message notification “failed : private method `split' called for nil:NilClass” usually occurs when you try to upload the csv files having data/content to the column other than existing header columns in the csv generated. So make sure that you haven't added data into the columns other than those created at the time of csv generation.