Fix: clicking an unsuitable piece of land in footpath drag mode will place a piece anyway

Specifically, path will be placed on the last tile that was suitable.

src/openrct2-ui/windows/Footpath.cpp

@@ -1193,6 +1193,7 @@ namespace OpenRCT2::Ui::Windows
             {
                 return;
             }
+            _provisionalFootpath.tiles.clear();
 
             auto mapPos = FootpathGetPlacePositionFromScreenPosition(screenCoords);
             if (!mapPos)