Export of unresolved monomer to everything except KET and IDT should cause specific error message (but it doesn't)

[AlexeyGirin]

Steps to Reproduce

1. Go to Macromolecules mode - Flex mode
2. Load using paste from clipboard IDT type: /i2AmPr/
   
3. Try to save canvas to Mol v2000 (and others unsupported - SDF v2000, SDF v3000, Daylight SMARTS, HELM)

Actual behavior

• Mol v2000 - Not fixed.
  
• SDF v2000 - Not fixed
  
• SDF v3000 - Not fixed
  
• Daylight SMARTS - Not fixed
  
• RXN v3000 - Not fixed
  

Expected behavior
System shows an error: Monomer /i2AmPr/ couldn't be saved to MDL Molfile V3000 format

As per requirements:

4. Attempt to save macromolecules with unknown monomers to file formats other than IDT and KET should result in error.
"Monomer /.../ couldn't be saved to .... format"

Versions

• Ketcher Version 2.27.0-rc.2 Build at 2024-11-12; 19:26:10
• Indigo Toolkit Version 1.26.0-rc.2.0-gfec30ecd8-wasm32-wasm-clang-19.0.0
• Chrome Version 131.0.6778.70 (Official Build) (64-bit)
• Win10

Issue found while testing - epam/ketcher#4431