Fix #8873: null dereference when trying to place footpath.

distribution/changelog.txt

@@ -1,6 +1,7 @@
 0.2.2+ (in development)
 ------------------------------------------------------------------------
 - Fix: [#5579] Network desync immediately after connecting.
+- Fix: [#8873] Potential crash when placing footpaths.
 
 0.2.2 (2019-03-13)
 ------------------------------------------------------------------------

src/openrct2/actions/FootpathSceneryPlaceAction.hpp

@@ -75,14 +75,14 @@ public:
         }
 
         auto tileElement = map_get_footpath_element(_loc.x / 32, _loc.y / 32, _loc.z / 8);
-        auto pathElement = tileElement->AsPath();
-
-        if (pathElement == nullptr)
+        if (tileElement == nullptr)
         {
             log_error("Could not find path element.");
             return MakeResult(GA_ERROR::INVALID_PARAMETERS, STR_CANT_POSITION_THIS_HERE);
         }
 
+        auto pathElement = tileElement->AsPath();
+
         // No change
         if (!(GetFlags() & GAME_COMMAND_FLAG_GHOST) && pathElement->GetAddition() == _pathItemType
             && !(pathElement->IsBroken()))

src/openrct2/world/Footpath.cpp

@@ -112,11 +112,11 @@ static bool entrance_has_direction(TileElement* tileElement, int32_t direction)
 
 TileElement* map_get_footpath_element(int32_t x, int32_t y, int32_t z)
 {
-    TileElement* tileElement;
-
-    tileElement = map_get_first_element_at(x, y);
+    TileElement* tileElement = map_get_first_element_at(x, y);
     do
     {
+        if (tileElement == nullptr)
+            break;
         if (tileElement->GetType() == TILE_ELEMENT_TYPE_PATH && tileElement->base_height == z)
             return tileElement;
     } while (!(tileElement++)->IsLastForTile());