Fix changing smallmap legend not updating viewport maps

src/smallmap_gui.cpp

@@ -487,8 +487,10 @@ static void NotifyAllViewports(ViewportMapType map_type)
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		if (w->viewport != nullptr)
-			if (w->viewport->zoom >= ZOOM_LVL_DRAW_MAP && w->viewport->map_type == map_type)
+			if (w->viewport->zoom >= ZOOM_LVL_DRAW_MAP && w->viewport->map_type == map_type) {
+				ClearViewportLandPixelCache(w->viewport);
 				w->InvalidateData();
+			}
 	}
 }
 

src/viewport_func.h

@@ -24,6 +24,7 @@ static const int TILE_HEIGHT_STEP = 50; ///< One Z unit tile height difference i
 void SetSelectionRed(bool);
 
 void ClearViewportCache(Viewport *vp);
+void ClearViewportLandPixelCache(Viewport *vp);
 void ClearViewportCaches();
 void DeleteWindowViewport(Window *w);
 void InitializeWindowViewport(Window *w, int x, int y, int width, int height, uint32 follow_flags, ZoomLevel zoom);