fix(container): fix a bug in GKE blue green upgrade policy (#16239) (#11464)

[upstream:99e25018be593e95bfd4b80c5fd00c4daad38d15]

Signed-off-by: Modular Magician <magic-modules@google.com>

Author: modular-magician

.changelog/16239.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+container: fixed a bug in `google_container_node_pool` that prevented creation when `blue_green_settings` was specified
+```

google-beta/services/container/resource_container_node_pool.go

@@ -1259,8 +1259,8 @@ func expandNodePool(d *schema.ResourceData, prefix string) (*container.NodePool,
 				return nil, fmt.Errorf("Blue-green upgrade settings may not be changed when blue-green strategy is not enabled")
 			}
 
-			if _, ok1 := blueGreenSettingsConfig["standard_rollout_policy"]; ok1 {
-				if _, ok2 := blueGreenSettingsConfig["autoscaled_rollout_policy"]; ok2 {
+			if s, ok1 := blueGreenSettingsConfig["standard_rollout_policy"]; ok1 && len(s.([]interface{})) > 0 {
+				if a, ok2 := blueGreenSettingsConfig["autoscaled_rollout_policy"]; ok2 && len(a.([]interface{})) > 0 {
 					return nil, fmt.Errorf("`standard_rollout_policy` and `autoscaled_rollout_policy` cannot be set at the same time")
 				}
 			}