fread skip=0 change breaks GGIRread tests

[tdhock]

#7484 breaks tests in https://rcdata.nau.edu/genomic-ml/data.table-revdeps/analyze/2026-03-02/GGIRread.txt

* checking tests ...
  Running 'testthat.R'
 ERROR
Running the tests in 'tests/testthat.R' failed.
Complete output:
  > library("testthat")
  > library("GGIRread")
  > test_check("GGIRread")
  Saving _problems/test_readActiwatchCount-21.R
  Saving _problems/test_readActiwatchCount-23.R
  Saving _problems/test_readActiwatchCount-25.R
  
    |                                                                            
    |=======================                                               |  33%
    |                                                                            
    |===============================================                       |  67%[ FAIL 3 | WARN 2 | SKIP 0 | PASS 355 ]
  
  == Failed tests ================================================================
  -- Failure ('test_readActiwatchCount.R:21:3'): Actiwatch awd is correctly read --
  Expected `nrow(D$data)` to equal 329.
  Differences:
  1/1 mismatches
  [1] 0 - 329 == -329
  -- Failure ('test_readActiwatchCount.R:23:3'): Actiwatch awd is correctly read --
  Expected `sum(D$data[, "counts"], na.rm = TRUE)` to equal 108864.
  Differences:
  1/1 mismatches
  [1] 0 - 108864 == -108864
  -- Failure ('test_readActiwatchCount.R:25:3'): Actiwatch awd is correctly read --
  Expected `sum(D$data[, "marker"], na.rm = TRUE)` to equal 2.
  Differences:
  1/1 mismatches
  [1] 0 - 2 == -2
  
  [ FAIL 3 | WARN 2 | SKIP 0 | PASS 355 ]
  Error:
  ! Test failures.
  Execution halted

this seems to be unexpected. @ben-schwen do you think data.table can fix this, or should we ask the revdep to fix?

[tdhock]

@aitap