`drop_empty_times` function in `se_root.py` evaluates dask-array values

[bert.coerver]

pywapor.enhancers.other.drop_empty_times calls .values on a lazy dask array, before saving the array to a netcdf. This can lead to problems with RAM and chunking.

Also check if this function is still required.

[bert.coerver]

fixed in https://bitbucket.org/cioapps/pywapor/commits/b10e422662d983a47cffd6cd6b8f89057536a06d