BalanceService throws NullPointerException

Problem:
If a product is closed that is traded before, the BalanceService throws a NullPointerException when calculating the balancingCosts in line 69:

balancingCosts = -deltaValue * (maxProductPrice.getPrice() + product.competition.balancingCostUnder)

Implications:
BalanceService is called in the CompetitionService. Due to the transactional = true property, the actions of the CompetitionService are rolled back and TimeAdvancement fails.

Todo:
Identify Null Object and assert NotNull