Released version failing R check

[schuemie]

This weekend's Github Actions failed R check for the latest released version of PatientLevelPrediction. I see:

  Running ‘testthat.R’ [15m/19m]
 [15m/19m] ERROR
Running the tests in ‘tests/testthat.R’ failed.
Last 13 lines of output:
  Error in `UseMethod("filter")`: no applicable method for 'filter' applied to an object of class "NULL"
  Backtrace:
      ▆
   1. ├─PatientLevelPrediction::createLearningCurve(...) at test-learningCurves.R:69:3
   2. │ └─base::lapply(...)
   3. │   └─PatientLevelPrediction (local) FUN(X[[i]], ...)
   4. │     └─PatientLevelPrediction:::learningCurveHelper(...)
   5. │       └─... %>% dplyr::pull()
   6. ├─dplyr::pull(.)
   7. ├─dplyr::tally(.)
   8. └─dplyr::filter(., .data$covariateValue != 0)

  [ FAIL 1 | WARN 14 | SKIP 1 | PASS 960 ]
  Error: Test failures
  Execution halted

[egillax]

Fixed in latest release