#19 unwanted selection feature ?

[Anonymous]

Soft : macPymol_0.98_b27

Os : MacOsX 10.3.7

After reading two molecules, in PDB format, one having
a chain identifyer, the other has not. Selecting Calphas in
both molecules. The commands rms or fit return error -
no atoms selected.

This seems to be due to the chain identifyer, since removing
this field from the file and readding it again, restores the
possibility
to have rms or fit commands work normaly.

Why not to allow fit or rms between molecules having different
chain IDs ?