Fix CHECK_CAST problem in the Jit.

The Jit has previously (and wrongly) assumed that because any CHECK_CAST
operation had previously succeeded in the interpreter, that the class
that check cast's object was being check against would already be resolved.
However, if the object being checked is NULL, no attempt is made to resolve
the class.  First bug flushed out by the Jit's stress mode (woohoo).
1 file changed