Error on running optimizer: Value cannot be null. Parameter name: value

[texasnomad]

My strategy works fine when backtesting. Yet when I run the optimizer, it throws this error:

Error on running optimizer: Value cannot be null. Parameter name: value

        private double risk = 0.0325;
        private int sL = 100; 
        private int tP = 100; 
        private int fileNumber = 1;

I read a previous thread on this issue. As you can see from my data types, they are all int and double.

        [Description("")]
        [GridCategory("Parameters")]
        public int FileNumber
        {
            get { return fileNumber; }
            set { fileNumber = value; }
        }

None of my inputs are named value. I checked properties. The only property I have that explicitly uses value is FileNumber.

The log file only contains one error. It says "Error on running optimizer: Value cannot be null." It's highlighted in green.