ACPICA: Properly handle NULL entries in _PRT return packages.

This change enables proper handling of NULL package entries in a _PRT
return value, during construction of the PCI routing table.
Lv Zheng.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/rscreate.c

@@ -292,7 +292,7 @@ acpi_rs_create_pci_routing_table(union acpi_operand_object *package_object,
 		/* 1) First subobject: Dereference the PRT.Address */
 
 		obj_desc = sub_object_list[0];
-		if (obj_desc->common.type != ACPI_TYPE_INTEGER) {
+		if (!obj_desc || obj_desc->common.type != ACPI_TYPE_INTEGER) {
 			ACPI_ERROR((AE_INFO,
 				    "(PRT[%u].Address) Need Integer, found %s",
 				    index,
@@ -305,7 +305,7 @@ acpi_rs_create_pci_routing_table(union acpi_operand_object *package_object,
 		/* 2) Second subobject: Dereference the PRT.Pin */
 
 		obj_desc = sub_object_list[1];
-		if (obj_desc->common.type != ACPI_TYPE_INTEGER) {
+		if (!obj_desc || obj_desc->common.type != ACPI_TYPE_INTEGER) {
 			ACPI_ERROR((AE_INFO,
 				    "(PRT[%u].Pin) Need Integer, found %s",
 				    index,
@@ -394,7 +394,7 @@ acpi_rs_create_pci_routing_table(union acpi_operand_object *package_object,
 		/* 4) Fourth subobject: Dereference the PRT.source_index */
 
 		obj_desc = sub_object_list[3];
-		if (obj_desc->common.type != ACPI_TYPE_INTEGER) {
+		if (!obj_desc || obj_desc->common.type != ACPI_TYPE_INTEGER) {
 			ACPI_ERROR((AE_INFO,
 				    "(PRT[%u].SourceIndex) Need Integer, found %s",
 				    index,