1-column file with NAs is read incorrectly

[st-pasha]

test0.txt

> data.table::fread("test0.txt")
         x0
  1: 656609
  2: 701231
  3: 733130
  4: 603634
  5: 355257
 ---       
872: 751956
873: 664415
874: 417495
875:  -2368
876: 955199

The file actually contains 999 rows -- all the NA values were silently skipped.

Note that small-size files with similar structures are read correctly:

> data.table::fread("A\n100\n200\n\n400")
     A
1: 100
2: 200
3:  NA
4: 400