Preview: CHEM are ignored without any messages or incorrect message while we save sequence with CHEM to IDT

[NadezhdaPeskun]

Steps to Reproduce
Scenario 1

1. Switch to Macro
2. Open KET file with CHEM
   ketcher (middle Chem).zip
3. try to save to IDT
   

Scenario 2

1. Open KET file with only CHEM
   ketcher (only Chems).zip

2. try to save to IDT >> empty IDT file is created
   ketcher (Empty from only Chems).zip

Scenario 3

1. Open KET file with only CHEM
   ketcher (Chem first).zip

2. try to save to IDT >> empty IDT file is created
   

Actual behavior
CHEM are ignored without any messages or incorrect error message while Chem linked to Sugar.

Expected behavior
According BA solution:
We should have message for CHEM as for Peptides if Chem is not in IDT library
"Cannot save molecule in IDT format - monomer(s)… doesn’t have IDT code."

Win11
Chrome: Version 123.0.6312.123 (Official Build) (64-bit)

Ketcher
[Version 2.22-rc.1] CI
[Indigo Toolkit] CI
Version 1.21.0-rc.1

[NadezhdaPeskun]

Should be moved to Indigo/

[NadezhdaPeskun]

Moved to Indigo:
epam/Indigo#1958