*fixed segfault (affects all flavors) where creating an expr object with more...

*fixed segfault (affects all flavors) where creating an expr object with more than MAX_VARS variables (currently set to 9) crashed pd when freeing the object. Example: create [expr 1;2;3;4;5;6;7;8;9;10] as opposed to [expr 1;2;3;4;5;6;7;8;9]. Former crashes when being freed (destroyed), while latter doesn't.