Conditional show/hide of objects is not possible in Office Reports.
This can be done in PixelPerfect templates using conditional formatting rules: How to Manage PixelPerfect Conditional Output Formats Using the Formatting Rules Editor
I have the same problem. Did you have any luck on working around this? The following attempt is ugly...
I tried conditionally hiding a pivot table when it has no data by overlaying an image of a text object. The pivot initially shows the empty dimension blocks so I set a calc condition to make it render only the nPrinting object name eg) <CH23> which is smaller to hide. Problem is that nPrinting does not appear to honor the setting of the background of the textbox as being transparent dynamimcally so you end up with a smallish white box overlaying your pivot when it does have data. I guess it depends on the data, which problem is worse.
Cheers - RAJT