Formula creates a String - Cell no longer blank/empty conditional formating

Hello,

I have a particular problem, I have a series of cells that have formulas to detect the checked values of a series of Check Boxes, creating conditional formatting and inserting 'N/A' in certain cells:

=IF([Assemblage Mecanique]8 = 1, "N/A", IF(Coupe8 = 1, "N/A", ""))

 after this check the cell retains a sting of nothing = ''''

 I have additional conditional formatting related to a check box to be performed on this same series of cells (show empty cells) - however this no longer works, as the conditional formatting condition of 'is Blank'  no longer functions.

I work around was inserting a ''-'' hyphen in the first formula, and this works for the second condition with 'Contains = -' 

=IF([Assemblage Mecanique]8 = 1, "N/A", IF(Coupe8 = 1, "N/A", "-"))

However, I don't what all the hyphens everywhere on my sheet.

the second screen capture shows a circled cell which should be red, as it is empty, however data is now "" from first formula.

Any other way of doing this in Smartsheet?

Paul