exception_action's ignorance of exceptions which stringify to empty string 

I'm not sure about how to find out that exception happened the right way. It seems to me that there is no simple way to check that $@ contains exactly empty string but not something which pretends to be. I am used to check that exception happened by writing "if( $@ ) {...}" ie ckecking for true/false. So my fix proposition may be good for me but not for all cases out there.