Please help: Validation of empty SOAP response in Script assertion.

I am new to soapUI. I have a soapUI request which sometimes gives empty response depending upon the input provided. This can also occur when I provide wrong End points for the request. I want to cover all test cases. So Please suggest how can I validate empty response in the script assertion. For example, I want to record this information in the output log file using following pseudocode.

if (Soap Response Empty)
  print "The webservice failed to execute due to empty response "

What condition should I provide in if clause to validate empty soap response.

Thanks
Ricky