Fixed some texture splatting issues with loading empty terrain cells

apps/openmw/mwrender/terrain.cpp

@@ -263,8 +263,7 @@ namespace MWRender
                 if ( it == indexes.end() )
                 {
                     //NB: All vtex ids are +1 compared to the ltex ids
-                    assert((int)ltexIndex >= 0 &&
-                           (int)store->landTextures->ltex.size() >= (int)ltexIndex - 1 &&
+                    assert( (int)store->landTextures->ltex.size() >= (int)ltexIndex - 1 &&
                            "LAND.VTEX must be within the bounds of the LTEX array");
                     
                     std::string texture;

components/esm/loadland.cpp

@@ -111,6 +111,8 @@ void Land::loadData(ESMReader &esm)
     }
     else
     {
+        landData->usingColours = false;
+        memset(&landData->textures, 0, 512 * sizeof(uint16_t));
         for (int i = 0; i < LAND_NUM_VERTS; i++)
         {
             landData->heights[i] = -256.0f * HEIGHT_SCALE;