despite what is said in the field description, an header (with empty cells) is actually generated even if the first line is empty.
The following patch fixes this issue.
This is the right way to do it!
Thanks! I made a minor modification to ensure that $variables['header'] wasn't empty, but this is good. I just committed to the 7.x-2.x branch.
The problem is still present in 6.x-2.x.
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