Ensure injected properties have public setters

src/Discord.Net.Commands/Utilities/ReflectionUtils.cs

@@ -20,7 +20,7 @@ namespace Discord.Commands
             var constructor = constructors[0];
             System.Reflection.ParameterInfo[] parameters = constructor.GetParameters();
             System.Reflection.PropertyInfo[] properties = typeInfo.DeclaredProperties
-                  .Where(p => p.CanWrite && p.GetCustomAttribute<DontInjectAttribute>() == null)
+                  .Where(p => p.SetMethod?.IsPublic == true && p.GetCustomAttribute<DontInjectAttribute>() == null)
                   .ToArray();
 
             return (map) =>