Failed to convert from cml file in case of only rgroup is present without rgroup reference

[ensemenova]

Steps to reproduce:

Send POST request to https://lifescience.opensource.epam.com/v2/indigo/convert
with following payload
{"struct":"<?xml version=\"1.0\" ?>\n<cml>\n <molecule title=\"\" />\n <Rgroup rgroupID=\"5\">\n <molecule>\n <atomArray>\n <atom id=\"a0\" elementType=\"C\" x2=\"3.8\" y2=\"-1.325\" />\n <atom id=\"a1\" elementType=\"C\" x2=\"3.8\" y2=\"-2.325\" />\n </atomArray>\n <bondArray>\n <bond atomRefs2=\"a0 a1\" order=\"1\" />\n </bondArray>\n </molecule>\n </Rgroup>\n</cml>\n","output_format":"chemical/x-mdl-molfile","options":{"smart-layout":true,"ignore-stereochemistry-errors":true,"mass-skip-error-on-pseudoatoms":false,"gross-formula-add-rsites":true}}
Actual result:
502 Bad Gateway Response status is returned

Expected result:
Correct rgroup molecule description, i.e.
`$MDL REV 1
$MOL
$HDR

$END HDR
$CTAB
0 0 0 0 0 999 V2000
M END
$END CTAB
$RGP
5
$CTAB
2 1 0 0 0 999 V2000
7.7000 -2.0750 0.0000 C 0 0 0 0 0 0 0 0 0 0 0 0
6.9929 -1.3679 0.0000 C 0 0 0 0 0 0 0 0 0 0 0 0
1 2 1 0 0 0
M END
$END CTAB
$END RGP
$END MOL`

[ensemenova]

Please notify Ketcher project when fixed