Impossible to calculate properties of the molecule patial selection (without R-Group) if molecule contains R-Group

Affected versions: Standalone

_Scenario 1._

Steps to reproduce:
1. Launch Ketcher.
2. Execute 'v2/indigo/calculate' with the following parameters:
struct
[ketcher (55).zip](https://github.com/epam/Indigo/files/6271289/ketcher.55.zip)
selected: [4, 5, 6, 7, 8, 9, 10, 11, 12]

Expected result: 'Chemical Formula', 'Molecular Weight', 'Exact Mass', 'Elemental Analysis' fields in the 'Calculated values' window are filled with the correct data.

Actual result: The 'Calculated values' window is opened with the following data: 'Chemical Formula' field is filled with the correct formula, 'Molecular Weight'/'Exact Mass'/'Elemental Analysis' fields are filled with 'mass: Cannot calculate mass for structure with pseudoatoms, template atoms or RSites' warning.

_Scenario 2._

Steps to reproduce:
1. Launch Ketcher.
2. Execute 'v2/indigo/calculate' with the following parameters:
struct
[ketcher56.zip](https://github.com/epam/Indigo/files/6296649/ketcher56.zip)
selected: [8, 9, 10]

Expected result: 'Chemical Formula', 'Molecular Weight', 'Exact Mass', 'Elemental Analysis' fields in the 'Calculated values' window are filled with the correct data.

Actual result: The 'Calculated values' window is opened with the following data: 'Chemical Formula' field is filled with incorrect data (C6H13()n), 'Molecular Weight'/'Exact Mass'/'Elemental Analysis' fields are filled with 'mass: Cannot calculate mass for structure with repeating units' warning.