ACPICA: Avoid use of invalid pointers in returned object field

During operand evaluation, ensure that the ReturnObj field is
cleared on error and only valid pointers are stored there.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/executer/exoparg1.c b/drivers/acpi/executer/exoparg1.c
index 252f10a..ab5c037 100644
--- a/drivers/acpi/executer/exoparg1.c
+++ b/drivers/acpi/executer/exoparg1.c
@@ -121,6 +121,7 @@
 
 	if ((ACPI_FAILURE(status)) || walk_state->result_obj) {
 		acpi_ut_remove_reference(return_desc);
+		walk_state->result_obj = NULL;
 	} else {
 		/* Save the return value */