Unclear error message when not logged in properly or driver is missing from login data

[marikaris]

Follow the first part of the manual for armadillo without logging in (if something went wrong with the login the error will also occur and it's unclear what went wrong:

login_data <- [data.frame](https://rdrr.io/r/base/data.frame.html)(
  server = "https://armadillo.test.molgenis.org", 
  storage = "https://armadillo-minio.test.molgenis.org", 
  driver = "ArmadilloDriver")
du.upload(
  cohort_id = 'gecko', 
  dict_version = '2_1', 
  dict_kind = 'core', 
  data_version = '1_0', 
  data_input_format = 'CSV',
  data_input_path = 'https://github.com/lifecycle-project/ds-upload/blob/master/inst/examples/data/WP1/data/all_measurements_v1_2.csv?raw=true',
  run_mode = "non_interactive"
)

Error:

 * Check released dictionaries
Error in if (ds_upload.globals$login_data$driver == du.enum.backends()$ARMADILLO) { : 
  argument is of length zero

Expected something like:
Armadillo driver not specified in login_data. Please take a look at your login_data and login using du.login(login_data = login_data).

[marikaris]

Solution:
In du.populate of populate.R make the check for opal an else if and add an else with a stop message.