ACPI: fix boot oops regression in thermal

Fix a memory overflow bug when copying
NULL internal package element object to external.

http://bugzilla.kernel.org/show_bug.cgi?id=10132



Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>