Merge branch 'master' into jgrpp

# Conflicts:
#	src/signs_cmd.cpp
#	src/station.cpp
#	src/station_cmd.cpp
#	src/town_cmd.cpp
#	src/viewport.cpp
#	src/waypoint.cpp
#	src/waypoint_cmd.cpp

src/station.cpp

@@ -167,7 +167,7 @@ Station::~Station()
 	CargoPacket::InvalidateAllFrom(this->index);
 
 	_station_kdtree.Remove(this->index);
-	if (_viewport_sign_kdtree_valid) _viewport_sign_kdtree.Remove(ViewportSignKdtreeItem::MakeStation(this->index, this->viewport_sign_kdtree_pt));
+	if (_viewport_sign_kdtree_valid && this->sign.kdtree_valid) _viewport_sign_kdtree.Remove(ViewportSignKdtreeItem::MakeStation(this->index));
 }