https://github.com/LLNL/GridDyn/blob/cf850abcc921f9f1bfea917ffc03a966d64c0a6a/src/griddyn/links/hvdc.cpp#L38
A dcLink can not be set to be a slack bus, so that statement throws unconditionally. This additionally leaks dcl.
This was added in 573966f, so I don't know what the expected behavior is.