[great-users] the library update tool

[Matthew J. Emerson]

If you remove some attributes from one of the metamodels used in your
GReAT transformation and then try to use the library update tool so that
your transformation will reflect this change, the tool will fail with an
"invalid cast" error.  However, before it fails it will set all of the
PatternClasses used in your rules to refer to null so you have to go
back and re-refer all of them.  This is a thing that should not be.

--Matt