Atom Fusion sign stuck during mission

[vrcalomino]

After playing a mission this sign appears every time:

If you start another mission without returning to the city, the sign will stay during the mission screen and you won't be able to do anything except restart.

Steps to reproduce:

• Start a world mission and win
• When you finish, start the next mission without returning to your city

Then you will get stuck and need to log out in order to solve it.