Revert "Core/Unit: Remove unused code as for 4.3.4"

This reverts commit 42e74822b8.

src/server/game/Entities/Unit/Unit.cpp

@@ -5329,6 +5329,10 @@ void Unit::setPowerType(Powers new_powertype)
         case POWER_ENERGY:
             SetMaxPower(POWER_ENERGY, uint32(std::ceil(GetCreatePowers(POWER_ENERGY) * powerMultiplier)));
             break;
+        case POWER_HAPPINESS:
+            SetMaxPower(POWER_HAPPINESS, uint32(std::ceil(GetCreatePowers(POWER_HAPPINESS) * powerMultiplier)));
+            SetPower(POWER_HAPPINESS, uint32(std::ceil(GetCreatePowers(POWER_HAPPINESS) * powerMultiplier)));
+            break;
     }
 }