CSV with empty values for integer fields

[Arun Chandrasekaran]

CSV with empty values for integer fields throws

(Row: 1, Col: 3) Unexpected end of input when converting from 
type string to type int

Code that parses the CSV:

```
import std.algorithm;
import std.array;
import std.csv;
import std.stdio;
import std.conv;
import std.range;

private struct IdentifyResult
{
     string probe;
     string target;
     int rank;
     int score;
     bool vendorMatch;
}

void main(string[] args)
{
     if (args.length < 2)
     {
         writeln("Usage: ", args[0], " <csv-file-1> ... 
<csv-file-n>");
         return;
     }

     foreach (i; 1 .. args.length)
     {
         try
         {
             auto arr = File(args[i], 
"r").byLine.joiner("\n").csvReader!IdentifyResult.array;
             writeln(args[i], "\tValid");
         }
         catch (std.csv.CSVException e)
         {
             writeln(e);
             writeln(args[i], "\tInvalid");
         }
     }
}
```

Input CSV file below

CSV header (just for reference, but not part of the CSV)
Probe,Target,rank,score,match/nomatch,datetime,position,score
```
LIP_0905_1230.nist,,,,FALSE,2017-09-05 23:24:37,,
LIP_0905_1230.nist,,,,FALSE,2017-10-12 11:37:29,,
LIP_0905_1230.nist,,,,FALSE,2017-10-12 11:51:03,,
LIP_0905_1230.nist,,,,FALSE,2017-10-12 12:07:21,,
LIP_0905_1230.nist,CRM_1012_1920.nist,1,9999,true,2017-10-12 
19:56:00,25,9999
LIP_0905_1230.nist,CRM_1012_1920.nist,1,9999,true,2017-10-13 
00:55:00,25,9999
LIP_0905_1230.nist,CRM_1013_0005.nist,2,9999,true,2017-10-13 
00:55:00,25,9999
LIP_0905_1230.nist,CRM_1012_1920.nist,1,9999,true,2017-10-18 
18:27:22,25,9999
LIP_0905_1230.nist,CRM_1013_0005.nist,2,9999,true,2017-10-18 
18:27:22,25,9999
LIP_0905_1230.nist,CRM_1013_0005.nist,1,9999,true,2017-10-20 
11:04:31,25,9999
```


Is there anyway to overcome this without modifying the original 
CSV?


Cheers,
Arun