Fix: SerializerSettings could reach be accessed in a state where ClientOptions were not defined

Author: acupofjose

Postgrest/Client.cs

@@ -70,6 +70,9 @@ public JsonSerializerSettings SerializerSettings
         {
             get
             {
+                if (options == null)
+                    options = new ClientOptions();
+
                 return new JsonSerializerSettings
                 {
                     ContractResolver = new CustomContractResolver(),

Postgrest/ClientOptions.cs

@@ -8,7 +8,7 @@ namespace Postgrest
     /// </summary>
     public class ClientOptions
     {
-        public string Schema { get; set; }
+        public string Schema { get; set; } = "public";
         public System.Globalization.DateTimeStyles DateTimeStyles = System.Globalization.DateTimeStyles.AdjustToUniversal;
         public string DateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.FFFFFFK";
         public Dictionary<string, string> Headers { get; set; } = new Dictionary<string, string>();