Unable to undo deleting a character in alignment

1. Open _common_data/regression/7273/web-clustalo.aln.
2. Delete the first symbol from the alignment.
3. Press Ctrl-Z (undo).
   Expected: no errors in the log, deletion canceled.
   Current state: undo doesn't work, errors in the log:
   [Core Services][ERROR] Trying to recover from error: Invalid modDetails '0 0 MSRMTDAKMIQQRMRGLTPEQRERLQ RALMPRIVEPYIAHIPHPKQQVFLTLNCKEAMYGGAAGGGKSDAVLMAALQYVDVPGY SALILRRTWPDLNAPGAILDRARTWLAGTDAVQRDGGRLFVFPSGA KLTFGYMQRDADKYKFQSAEYQFIGFDELTHFEEGQYTYLFSRLRRPDLVCLNCGN AVRRYAGHKTWAHTGRKAGKRCSRIFPDPKVIQQYPPSEKDELTIFDIPLRMRSA TNPGGIGNEWVKQRFVNPESREPDSVFVPAKLVDNPSLDRDSYRESLSHLTEVDRQR LENGDWDIAESGDFFKRHNFKVIDHPSQAERGEVRV RFWDLAATEGGGDWTAGCLLLFKKDGTYEVQDMVRVQSSGG KIESLIAQTAQVDGRDVMIRMEQEPGSSGKNIIDHYARNVLYGYDFDGVRSTGSKET RAYPVAVSSEKGHISIVLGEHTRAFLNELDAFPTGANDDMVDALSGAFAE AAFARRGRLLA MSRMTDAKMIQQRMRGLTPEQRERLQ RALMPRIVEPYIAHIPHPKQQVFLTLNCKEAMYGGAAGGGKSDAVLMAALQYVDVPGY SALILRRTWPDLNAPGAILDRARTWLAGTDAVQRDGGRLFVFPSGA KLTFGYMQRDADKYKFQSAEYQFIGFDELTHFEEGQYTYLFSRLRRPDLVCLNCGN AVRRYAGHKTWAHTGRKAGKRCSRIFPDPKVIQQYPPSEKDELTIFDIPLRMRSA TNPGGIGNEWVKQRFVNPESREPDSVFVPAKLVDNPSLDRDSYRESLSHLTEVDRQR LENGDWDIAESGDFFKRHNFKVIDHPSQAERGEVRV RFWDLAATEGGGDWTAGCLLLFKKDGTYEVQDMVRVQSSGG KIESLIAQTAQVDGRDVMIRMEQEPGSSGKNIIDHYARNVLYGYDFDGVRSTGSKET RAYPVAVSSEKGHISIVLGEHTRAFLNELDAFPTGANDDMVDALSGAFAE AAFARRGRLLA ""'! at C:\BuildAgent\work\release_branch\src\corelibs\U2Core\src\dbi\U2DbiPackUtils.cpp:568
   [Core Services][ERROR] An error occurred during reverting replacing sequence data!
   [Core Services][TRACE] Can't undo a single step: 'An error occurred during reverting replacing sequence data!'!
   [Core Services][ERROR] Can't undo an operation for the object!
   [Core Services][ERROR] Trying to recover from error: Can't undo an operation for the object! at C:\BuildAgent\work\release_branch\src\corelibs\U2View\src\UndoRedoFramework.cpp:114

In ClustalW format, a sequence line can contain a white space between symbols in the sequence and a cumulative number of residues for the sequences. In the file, instead of a space, there was a horizontal tab.