You need to put this line : Property Name="PopulationSystemLevel" Operation="Force" Value="$(SystemLevel)"/ in SimulationDescriptors[Population] within the simulation descriptor ClassPopulationPlanet. You should not remove any other line. Only tested for modernization up to level 2. Do not forget to put the < before Property and > after /
You need to put this line : Property Name="PopulationSystemLevel" Operation="Force" Value="$(SystemLevel)"/ in SimulationDescriptors[Population] within the simulation descriptor ClassPopulationPlanet. You should not remove any other line. Only tested for modernization up to level 2. Do not forget to put the < before Property and > after /