Incorrect missedBlocks update after delete last block of round

[4miners]

Scenario

Round rollback when forger of last block of round is replaced in last block of round.

• unvote deletage A, vote delegate B into 101 at last block of round
• delete last block of round

Expected behavior

• delegate B should have missedBlocks equal to 0

Actual behavior

• delegate B have missedBlocks equal to -1

Steps to reproduce

Run rounds functional system tests.

Which version(s) does this affect? (Environment, OS, etc...)

1.0.0, 0.9.12 not tested