make_assembly behaviour change from 0.6.5 to 0.7.5

[jackdent]

If I run the following script with this CIF file:

from pathlib import Path

import gemmi


def load_structure(cif_path: Path):
    block: gemmi.cif.Block = gemmi.cif.read(str(cif_path))[0]
    structure: gemmi.Structure = gemmi.make_structure_from_block(block)
    structure.remove_waters()
    structure.transform_to_assembly(
        assembly_name="1",
        how=gemmi.HowToNameCopiedChain.Dup,
    )
    return structure


load_structure(Path("./1AK5.cif"))

On 0.6.5 the file loads successfully, but on 0.7.5 I get RuntimeError: no subchain C:

root@devbox-jack:/workspaces/models# uv pip install gemmi==0.6.5 && python gemmi_test.py 
Using Python 3.11.15 environment at: /opt/venv
Audited 1 package in 3ms
root@devbox-jack:/workspaces/models# uv pip install gemmi==0.7.5 && python gemmi_test.py 
Using Python 3.11.15 environment at: /opt/venv
Resolved 1 package in 1ms
Uninstalled 1 package in 1ms
Installed 1 package in 8ms
 - gemmi==0.6.5
 + gemmi==0.7.5
Traceback (most recent call last):
  File "/workspaces/models/gemmi_test.py", line 17, in <module>
    load_structure(Path("./1AK5.cif"))
  File "/workspaces/models/gemmi_test.py", line 10, in load_structure
    structure.transform_to_assembly(
RuntimeError: no subchain C

Note that if I change the order of removing the waters and transforming assembly, the test case also passes on 0.7.5:

from pathlib import Path

import gemmi


def load_structure(cif_path: Path):
    block: gemmi.cif.Block = gemmi.cif.read(str(cif_path))[0]
    structure: gemmi.Structure = gemmi.make_structure_from_block(block)
    structure.transform_to_assembly(
        assembly_name="1",
        how=gemmi.HowToNameCopiedChain.Dup,
    )
    structure.remove_waters() # N.B. order changed!
    return structure


load_structure(Path("./1AK5.cif"))

Is this change expected? What is the "right" order to call these operations in?