Silence ivar warning in rubygems test suite

This is regarding #6 -- Using `defined?` works. Using `@path_take.nil?` didn't work for me. I think because we are still trying to access an uninitialized ivar.

The tests pass with the change. However `defined?` is only checking if `@path-take` is umm defined not if it's value is nil. Could a situation arise where this ivar is initialized but later becomes nil?