write_to_file does not close file

[SchroederSa]

When executing these lines twice, the write call fails.

laser = Laser("rt", (-100e-6, -40e-6/sc.c), (100e-6, 40e-6/sc.c), (Nr, Nz), lasy_profile, n_azimuthal_modes = 2)
laser.write_to_file("test/laser")

    110 env.reset_dataset(dataset)
    111 env.store_chunk(data)
--> 113 series.flush()

RuntimeError: [HDF5] Internal error: Failed to create HDF5 file

The reason for this is, that the written file is not closed with series.close()

cc @ax3l