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>
diff --git a/drivers/acpi/utilities/utobject.c b/drivers/acpi/utilities/utobject.c
index 76ee766..e08b3fa 100644
--- a/drivers/acpi/utilities/utobject.c
+++ b/drivers/acpi/utilities/utobject.c
@@ -432,7 +432,7 @@
 	 * element -- which is legal)
 	 */
 	if (!internal_object) {
-		*obj_length = 0;
+		*obj_length = sizeof(union acpi_object);
 		return_ACPI_STATUS(AE_OK);
 	}