C# Unity can't cast integer represented enum value.

C# Unity can't cast integer represented enum value.

```
namespace MyGame;

enum CommandType : byte {
	None = 0,
}

table Command {
	id:int;
	type:CommandType;
}
```

then generate c# files. it'll output compile error like these.

```
Assets/MyGame/Command.cs(18,39): error CS1041: Identifier expected
Assets/MyGame/Command.cs(18,39): error CS1737: Optional parameter cannot precede required parameters

16:   public static Offset<Command> CreateCommand(FlatBufferBuilder builder,
17:   int id = 0,
18:   CommandType type = (CommandType)0) {
```