getFasta should not give a response to the preservation of nucleotide compounds with other monomers

[AnnaKosol]

Steps to Reproduce

1. Open Macromolecules mode - Flex mode
2. Open Console
3. Add schema from file Schema nucleotide with chem with different connections.ket.zip
4. Type in the Console ketcher.getFasta()

Expected behavior An error should be displayed

Actual behavior A response with the code is displayed

The issue is the same for these files: Schema nucleotide with base with different connections.ket.zip Schema nucleotide with peptide with different connections.ket.zip Schema nucleotides with phosphate with different connections.ket.zip Schema nucleotide with sugar with different connections.ket.zip

Environment details: Ketcher Version 2.23.0-rc.2 Build at 2024-07-10; 19:39:22 Indigo Version 1.22.0-rc.2.0-ga21fb5d8f-wasm32-wasm-clang-19.0.0 Chrome Версия 126.0.6478.127 (Официальная сборка), (arm64) MacOs Sonoma 14.5 Issue found for https://github.com/epam/ketcher/issues/4382

[AliaksandrDziarkach]

Paned to fix with Fasta variant monomers support