[Dbix-class] Schema reference object disapears from my resultset when building collections

[Brandon Black]

Usually the cause of these sorts of problems is that your only copy of
$schema has gone out of scope before the failing use of the resultset.
 The $schema object that the resultset came from has to stay in scope
somewhere, if it is freed, the resultset won't work anymore (this is
due to a weak backreference, so that perl garbage collection can clean
up schemas and resultsets, etc).

-- Brandon