hg: jdk10/hs: 8189794: Assert in InstanceKlass::cast called from Exceptions::new_exceptions

[coleen.phillimore at oracle.com]

Changeset: 54b78d6243c5
Author:    coleenp
Date:      2017-10-24 08:29 -0400
URL:       http://hg.openjdk.java.net/jdk10/hs/rev/54b78d6243c5

8189794: Assert in InstanceKlass::cast called from Exceptions::new_exceptions
Summary: Fix call to InstanceKlass::cast to only be after verifying class is non-null.
Reviewed-by: dholmes, sspitsyn

! src/hotspot/share/utilities/exceptions.cpp