Fixed a NULL ptr failure in GridStructGen.

When the descendant generator returned a NULL structure, the generator would crash. Now it uses a special cEmptyStructure class instead.

src/Generating/GridStructGen.cpp

@@ -9,6 +9,34 @@
 
 
 
+///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// cEmptyStructure:
+
+/** A cStructure descendant representing an empty structure.
+Used when the generator descended from cGridStructGen doesn't return any structure, to keep at least the
+Origin coords so that the structure isn't queried over and over again. */
+class cEmptyStructure :
+	public cGridStructGen::cStructure
+{
+	typedef cGridStructGen::cStructure super;
+	
+public:
+	cEmptyStructure(int a_OriginX, int a_OriginZ) :
+		super(a_OriginX, a_OriginZ)
+	{
+	}
+	
+protected:
+	virtual void DrawIntoChunk(cChunkDesc & a_ChunkDesc) override
+	{
+		// Do nothing
+	}
+} ;
+
+
+
+
+
 cGridStructGen::cGridStructGen(
 	int a_Seed,
 	int a_GridSizeX, int a_GridSizeZ,
@@ -81,7 +109,12 @@ void cGridStructGen::GetStructuresForChunk(int a_ChunkX, int a_ChunkZ, cStructur
 			}  // for itr - a_Structures[]
 			if (!Found)
 			{
-				a_Structures.push_back(CreateStructure(OriginX, OriginZ));
+				cStructurePtr Structure = CreateStructure(OriginX, OriginZ);
+				if (Structure.get() == NULL)
+				{
+					Structure.reset(new cEmptyStructure(OriginX, OriginZ));
+				}
+				a_Structures.push_back(Structure);
 			}
 		}  // for z
 	}  // for x

src/Generating/GridStructGen.h

@@ -39,14 +39,6 @@ class cGridStructGen :
 	public cFinishGen
 {
 public:
-	cGridStructGen(
-		int a_Seed,
-		int a_GridSizeX, int a_GridSizeZ,
-		int a_MaxStructureSizeX, int a_MaxStructureSizeZ,
-		size_t a_MaxCacheSize
-	);
-	
-protected:
 	/** Represents a single structure that occupies the grid point. Knows how to draw itself into a chunk. */
 	class cStructure
 	{
@@ -75,6 +67,14 @@ protected:
 	typedef std::list<cStructurePtr> cStructurePtrs;
 	
 	
+	cGridStructGen(
+		int a_Seed,
+		int a_GridSizeX, int a_GridSizeZ,
+		int a_MaxStructureSizeX, int a_MaxStructureSizeZ,
+		size_t a_MaxCacheSize
+	);
+	
+protected:
 	/** Seed for generating the semi-random grid. */
 	int m_Seed;