I believe ForAll(RevenuePreDefinedCollection, If(Or(IsBlank(CategoryCC),CategoryCC.Selected.Value<>"Select...")), Patch('Revenue Pre-Defined Categories', Defaults('Revenue Pre-Defined Categories'), {Title: CategoryCC, AmountEach: AmountEachCC, Quantity: QuantityCC, Subtotal: SubtotalCC, MasterID: Form1.LastSubmit.ID}))) should work.
If I'm correct, the If statement reduces to true if CategoryCC is blank or does not contain the Selected Value "Select...". and when the statement is true, then the patch will run. Give it a try and see if it works.