fix panic in google_sql_database_instance datasource (#15709)

Author: shuyama1

mmv1/third_party/terraform/services/sql/resource_sql_database_instance.go.tmpl

@@ -2717,7 +2717,11 @@ func resourceSqlDatabaseInstanceImport(d *schema.ResourceData, meta interface{})
 	return []*schema.ResourceData{d}, nil
 }
 
-func flattenSettings(settings *sqladmin.Settings, iType string, d *schema.ResourceData) []map[string]interface{} {
+func flattenSettings(settings *sqladmin.Settings, iType string, d *schema.ResourceData) []map[string]interface{} {	
+	if settings == nil {
+		return nil
+	}
+
 	data := map[string]interface{}{
 		"version":                          settings.SettingsVersion,
 		"tier":                             settings.Tier,