Sure, the usual way to do this is to run a blank stats command, something like;
SEARCH COMMAND WITH CHARTING | append [|stats count | eval Fieldname=""]
This way you get a blank row appended which will force a blank chart to render. You can play around with this to match your exact search and perhaps include it within the main search and check for null values etc for when to display.
No, AFAIK, but that would be a nice enhancement request. You can submit one here