More work on nullable references

src/Umbraco.Infrastructure/Persistence/UmbracoDatabase.cs

@@ -27,9 +27,9 @@ namespace Umbraco.Cms.Infrastructure.Persistence
         private readonly ILogger<UmbracoDatabase> _logger;
         private readonly IBulkSqlInsertProvider _bulkSqlInsertProvider;
         private readonly DatabaseSchemaCreatorFactory _databaseSchemaCreatorFactory;
-        private readonly RetryPolicy _connectionRetryPolicy;
-        private readonly RetryPolicy _commandRetryPolicy;
-        private readonly IEnumerable<IMapper> _mapperCollection;
+        private readonly RetryPolicy? _connectionRetryPolicy;
+        private readonly RetryPolicy? _commandRetryPolicy;
+        private readonly IEnumerable<IMapper>? _mapperCollection;
         private readonly Guid _instanceGuid = Guid.NewGuid();
         private List<CommandInfo> _commands;
 
@@ -49,9 +49,9 @@ namespace Umbraco.Cms.Infrastructure.Persistence
             ILogger<UmbracoDatabase> logger,
             IBulkSqlInsertProvider bulkSqlInsertProvider,
             DatabaseSchemaCreatorFactory databaseSchemaCreatorFactory,
-            RetryPolicy connectionRetryPolicy = null,
-            RetryPolicy commandRetryPolicy = null,
-            IEnumerable<IMapper> mapperCollection = null)
+            RetryPolicy? connectionRetryPolicy = null,
+            RetryPolicy? commandRetryPolicy = null,
+            IEnumerable<IMapper>? mapperCollection = null)
             : base(connectionString, sqlContext.DatabaseType, provider, sqlContext.SqlSyntax.DefaultIsolationLevel)
         {
             SqlContext = sqlContext;