Fix for crash on RPC Start when no wallet in node.

Stratis.Bitcoin/Features/RPC/RPCFeature.cs

@@ -1,12 +1,12 @@
-using System;
-using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Hosting;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Stratis.Bitcoin.Builder;
 using Stratis.Bitcoin.Builder.Feature;
 using Stratis.Bitcoin.Configuration;
 using Stratis.Bitcoin.Features.RPC.Controllers;
 using Stratis.Bitcoin.Utilities;
+using System;
 
 namespace Stratis.Bitcoin.Features.RPC
 {
@@ -45,7 +45,18 @@ public override void Start()
                         // also copies over singleton instances already defined
                         foreach (var service in this.fullNodeBuilder.Services)
                         {
-                            var obj = this.fullNode.Services.ServiceProvider.GetService(service.ServiceType);
+                            object obj = null;
+
+                            try
+                            {
+                                obj = this.fullNode.Services.ServiceProvider.GetService(service.ServiceType);
+                            }
+                            catch (InvalidOperationException)
+                            {
+                                this.logger.LogWarning("Unable to copy service {service} from Full Node to RPC. Service injection skipped.", service.ServiceType.ToString());
+                                obj = null;
+                            }
+
                             if (obj != null && service.Lifetime == ServiceLifetime.Singleton && service.ImplementationInstance == null)
                             {
                                 collection.AddSingleton(service.ServiceType, obj);