Currently selected troop gets deselected if previous troop completes tower slots

[LpTrip]

Build: 8578

Repro steps:

1. Start the game.
2. Play any skirmish map.
3. Build a watchtower and train 4 militia.
4. Split them in groups of 2 as shown in the image below.
5. Order one troop to access the tower and then select the other troop.

Result: second troops gets deselected as soon tower slots are completed. This issue also occurs with guardtower and with other types of units.