Always init ExtensionData & fix BaseInteractionRequestData inheritance

Libraries/SPTarkov.Server.Core/Models/Eft/HttpResponse/GetBodyResponseData.cs

@@ -6,7 +6,7 @@ namespace SPTarkov.Server.Core.Models.Eft.HttpResponse;
 public record GetBodyResponseData<T>
 {
     [JsonExtensionData]
-    public Dictionary<string, object>? ExtensionData { get; set; }
+    public Dictionary<string, object> ExtensionData { get; init; } = [];
 
     [JsonPropertyName("err")]
     public BackendErrorCodes? Err { get; set; }

Libraries/SPTarkov.Server.Core/Models/Eft/HttpResponse/NullResponseData.cs

@@ -5,7 +5,7 @@ namespace SPTarkov.Server.Core.Models.Eft.HttpResponse;
 public record NullResponseData
 {
     [JsonExtensionData]
-    public Dictionary<string, object>? ExtensionData { get; set; }
+    public Dictionary<string, object> ExtensionData { get; init; } = [];
 
     [JsonPropertyName("err")]
     public int? Err { get; set; }