[side_drop] sides go to idle, not human (fix bug 21459)

since idle sides don't get initialized until someone takes control
this alleviates 21459. it might possibly aggravate 21397, if that
bug is not fixed by correcting save files with unintialized sides

src/playturn.cpp

@@ -333,9 +333,9 @@ turn_info::PROCESS_DATA_RESULT turn_info::process_network_data(const config& cfg
 
 					{
 						// Server thinks this side is ours now so in case of error transferring side we have to make local state to same as what server thinks it is.
-						tm.make_human();
-						tm.set_current_player("human"+side_drop);
-						if (have_leader) leader->rename("human"+side_drop);
+						tm.make_idle();
+						tm.set_current_player("idle"+side_drop);
+						if (have_leader) leader->rename("idle"+side_drop);
 					}
 
 					const size_t index = static_cast<size_t>(action - first_observer_option_idx);