ee_utils_sak_copy() wrongly states that file is copied even if not existing

[MatthieuStigler]

Running ee_utils_sak_copy("any file") on a non existing file will still delivers a positive message that the file was successfully copied:

library(rgee)
reticulate::use_condaenv("~/programs/anaconda3/envs/ee")
file.exists("any file")
#> [1] FALSE
ee_utils_sak_copy("any file")
#> SaK copy successfully

^{Created on 2025-06-30 with reprex v2.1.1}