fix: Resolve compile-time warnings in first-party code

[andy5995]

• Fix logic bug in unit_type.cpp: dangling string expression was a no-op (missing desc += prefix); result was silently discarded
• Fix -Wterminate in renderer.cpp: throwing from a destructor calls terminate() in C++11; log and swallow instead
• Fix -Wformat-overflow in main.cpp (30 sites): NULL passed as %s argument to printf causes UB; replaced with ""
• Fix -Wreorder in network_types.cpp and menu_state_root.cpp: member initializer order didn't match declaration order
• Fix -Wswitch in 11 switch statements across commander.cpp, game.cpp, core_data.cpp, gui.cpp, unit_updater.cpp, client_interface.cpp, server_interface.cpp, network_message.cpp, menu_state_mods.cpp, and glest_map_editor (main.cpp, program.cpp): add default: break; for intentionally unhandled enum values