Merge branch 'master' into jgrpp

# Conflicts:
#	src/3rdparty/fmt/core.h
#	src/command_type.h
#	src/console_cmds.cpp
#	src/core/overflowsafe_type.hpp
#	src/landscape.cpp
#	src/network/network.cpp
#	src/newgrf_object.h
#	src/object_cmd.cpp
#	src/order_gui.cpp
#	src/saveload/vehicle_sl.cpp
#	src/script/api/script_industrytype.cpp
#	src/script/api/script_object.hpp
#	src/script/api/script_town.cpp
#	src/table/object_land.h
#	src/timetable_cmd.cpp
#	src/tree_cmd.cpp
#	src/vehicle_gui.cpp
#	src/window.cpp

src/newgrf_gui.cpp

@@ -1468,6 +1468,9 @@ private:
 				this->avails.push_back(c);
 			} else {
 				const GRFConfig *best = FindGRFConfig(c->ident.grfid, HasBit(c->flags, GCF_INVALID) ? FGCM_NEWEST : FGCM_NEWEST_VALID);
+				/* Never triggers; FindGRFConfig returns either c, or a newer version of c. */
+				assert(best != nullptr);
+
 				/*
 				 * If the best version is 0, then all NewGRF with this GRF ID
 				 * have version 0, so for backward compatibility reasons we