delete_cols retaining data from deleted column when adjacent cell is blank
*Created originally on Bitbucket by [cehess (Chris Hess)](https://bitbucket.org/%7B7d86e34f-1aaa-4512-87f4-6a8c799fee5f%7D/)* Scenario: A spreadsheet with column A and column B. Column B includes some empty cells. When column A is deleted, all cells from column B that contain values are properly reflected in their new position in column A. However, blank cells from column B continue to reflect their original data from column A. Files attached. I did not test how delete_rows behaves in a similar situation. *Attachments:* [delete_cols_test_out.xlsx](/uploads/3878a711e57bd2ddf91f582ca42be4d0/delete_cols_test_out.xlsx)[delete_cols_test.py](/uploads/bd5872b62814ee8a0ca04e13f39cce4c/delete_cols_test.py)[delete_cols_test.xlsx](/uploads/198cee59d203fad86df1131ac27a66ca/delete_cols_test.xlsx)
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