The lattice builder won't check for element information if loaded from CIF

[CalCraven]

Bug summary

Element information in a CIF file is not loaded properly.

Code to reproduce the behavior

Please include a code snippet that can be used to reproduce this bug.

from mbuild.lattice import load_cif

lattice_cif_ETV_triclinic = load_cif( #this cif file has oxygen atoms in it
             file_or_path=get_fn("ETV_triclinic.cif")
)
ETV_triclinic = lattice_cif_ETV_triclinic.populate(x=1, y=1, z=1)
for part in ETV_triclinic.particles():
    assert part.element

Software versions

• Which version of mBuild are you using? (python -c "import mbuild as mb; print(mb.__version__)") 0.15.1
• Which version of Python (python --version)? 3.9
• Which operating system? MacOS