Update ParseCSVLine.cs to fix the behaviour in case of null or missing values

[asad4237]

I am using this program in stock prediction and this is a common scenario in the stock prediction that value of some new ticker may be unknown.

First case: first expected value is missing in CSV, In this case, the first line was having less number of columns than the current line.
//Sample data
//0,0,
//0,1,1
//1,0,1
//1,1,0
Second case: after first-line expected value is missing in CSV, In this case, the previous line was having more columns than current line, So reset the array so that it does not carry the old values into missing column.
//Sample data
//0,0,0
//0,1,
//1,0,1
//1,1,0

This fix is going to treat missing values as "?" which is a native representation of missing values in Encog Framework