QPlainTextEdit wrong position when cursor move to next row after delete.

The case when bug appear is like that:
1. There is document with long lines
2. I move to next line and set at specific position in that line
3. I mark part of that line from position to the end of line
4. I delete that selection
5. I move to next line
Then seems that position in next line is calculated with ignorance fact of deletion - it seems that it calculates position in next line basing of position end of line before deletion.