Column empty and not being processed when top row's cell is empty #643

Ref #593

Describe the bug
Column is not being pulled through into dataframe
When uploading an excel which has the topmost row empty for a given column, that column will not come throw

To Reproduce
Steps to reproduce the behavior:

1. Create an excel which has headers and the top most row for column X is empty
2. dfd.readExcel
3. console.log(df.columns)
4. See column missing

Expected behavior
The column should be there

Desktop (please complete the following information):

• OS: MacOS
• Browser Safari
• Version 1.1.2