SAFE_POINT on a character drag'n'drop in the Sanger Reads Editor

Scenario to reproduce:

1. Open an MCA.
2. Click to the last symbol of the read.
3. Drag and drop it to the right.
   Current state: when the symbol is out of the reference boundaries, trailing gaps are added to the reference. But there are many errors in the log like

   [ERROR][13:18] Trying to recover from error: Failed to update visible range. Range is out of the sequence range! at src/ov_sequence/GSequenceLineView.cpp:446