Create APIKeys as null if file read fails

Program.cs

@@ -18,7 +18,7 @@ var connectionString = new SqliteConnectionStringBuilder(builder.Configuration.G
 builder.Services.AddDbContext<TodoContext>(options => options.UseSqlite(connectionString));
 
 //setup APIKey validation using apikey.json file
-ApiKeys apiKeys = new();
+ApiKeys? apiKeys = null;
 try
 {
     string? apiKeyFilename = builder.Configuration.GetValue<string>("APIKeyFile");