IF Statemet returning error (#VALUE!) [Subtracting from ""]

Hi,

the following 'if' statement returns a #VALUE! error if the target cells have no value:

=IF(G19-H19<0,G19-H19,"")

Here's what I tried to fix it, which was not successful.

=IF(G19="",IF(H19="","",IF(G19-H19>0,G19-H19,"")),IF(G19-H19>0,G19-H19,""))

I understand that subtracting a "" value doesn't make any logical sense to excel, but is there a way to get excel to 'think' that these "" values represent 0?