Merge branch 'save_ext' into jgrpp

# Conflicts:
#	Makefile.src.in
#	findversion.sh
#	projects/determineversion.vbs
#	src/gamelog.cpp
#	src/gamelog_internal.h
#	src/lang/german.txt
#	src/lang/korean.txt
#	src/network/core/config.h
#	src/network/network.cpp
#	src/network/network_udp.cpp
#	src/rev.h
#	src/saveload/afterload.cpp
#	src/saveload/company_sl.cpp
#	src/saveload/depot_sl.cpp
#	src/saveload/gamelog_sl.cpp
#	src/saveload/misc_sl.cpp
#	src/saveload/order_sl.cpp
#	src/saveload/saveload.cpp
#	src/saveload/station_sl.cpp
#	src/saveload/town_sl.cpp
#	src/saveload/vehicle_sl.cpp
#	src/table/settings.ini
#	src/viewport.cpp

src/group_cmd.cpp

@@ -718,6 +718,8 @@ CommandCost CmdSetGroupLivery(TileIndex tile, DoCommandFlag flags, uint32 p1, ui
 
 	if (g == NULL || g->owner != _current_company) return CMD_ERROR;
 
+	if (colour >= COLOUR_END && colour != INVALID_COLOUR) return CMD_ERROR;
+
 	if (flags & DC_EXEC) {
 		if (primary) {
 			SB(g->livery.in_use, 0, 1, colour != INVALID_COLOUR);