- Fixed regression where new methods on :class:`.ResultProxy` used

- Fixed regression where new methods on :class:`.ResultProxy` used
by the ORM :class:`.Query` object (part of the performance
enhancements of :ticket:`3175`) would not raise the "this result
does not return rows" exception in the case where the driver
(typically MySQL) fails to generate cursor.description correctly;
an AttributeError against NoneType would be raised instead.
fixes #3481