fixes the bug introduced in a2ea2ae0c1b57275e1004916436cb6e554cf9fd6 where the _curtailment wasn't properly assigned to network.timeseries.curtailment, this caused problems with _check_curtailment() function
fixes the bug introduced in a2ea2ae0c1b57275e1004916436cb6e554cf9fd6 where the _curtailment wasn't properly assigned to network.timeseries.curtailment, this caused problems with _check_curtailment() function

openego/eDisGo,openego/eDisGo