MediatR PipelineBehavior error message Unable to resolve service for type 'FluentValidation.IValidator`1

Question

I have this ValidationBehavior

public sealed class ValidationBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    private readonly IValidator<TRequest> _validator;

    public ValidationBehavior(IValidator<TRequest> validator)
    {
        _validator = validator;
    }

    public async Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate<TResponse> next)
    {
        _validator.ValidateAndThrow(request);
        return await next();
    }
}  

I have this handler

public class RemoveCurrencyHandler : IRequestHandler<RemoveCurrencyCommand, Unit>
{
    private readonly ApplicationContext _context;

    public RemoveCurrencyHandler(ApplicationContext context)
    {
        _context = context;
    }

    public async Task<Unit> Handle(RemoveCurrencyCommand request, CancellationToken cancellationToken)
    {
        var currency = await _context.Currency.FindAsync(request.Id);

        if (currency is null)
            throw new KeyNotFoundException();

        _context.Remove(currency);
        await _context.SaveChangesAsync();
        return Unit.Value;
    }
}  

I'm getting error message Unable to resolve service for type 'FluentValidation.IValidator' everytime I call this handler, now obviously I know the reason is because I'm missing the validator, so it goes away if I add this

public class RemoveCurrencyValidator : AbstractValidator<RemoveCurrencyCommand>
{

}  

but not all my handler need a Validator, so I don't want to add empty Validator class to handler that doesn't need it. Is there any alternative?