--no-number-headers does not work correctly if header line is not at the start of the file

[gwsw]

Steps to reproduce:

1. Run seq 100 | less -N --no-number-headers
2. Enter 10j
3. Enter --header=1

Expected result: First lines on the screen should be

    11
  1 12
  2 13
  3 14

Actual result: First lines on the screen are

 10 11
 11 12
 12 13
 13 14

[gwsw]

Fixed in 47a7b8e25a43bf0e48d775da38c5c897cb4adcee in the post659 branch.