Fix compilation

src/common/rendering/hwrenderer/data/hw_meshbuilder.cpp

@@ -1,8 +1,22 @@
 
+#include "levelmeshhelper.h"
 #include "hw_meshbuilder.h"
 #include "hw_mesh.h"
 #include "v_video.h"
 
+
+struct NullLevelMeshUpdater : UpdateLevelMesh
+{
+	virtual void SectorChanged(void *sector) {};
+
+	virtual void SideChanged(void *side) {};
+};
+
+static NullLevelMeshUpdater nullUpdater;
+
+UpdateLevelMesh* LevelMeshUpdater = &nullUpdater;
+
+
 MeshBuilder::MeshBuilder()
 {
 	Reset();

src/levelmeshhelper.h

@@ -1,15 +1,12 @@
+#pragma once
 // level mesh helper
 // this is a minimal include to keep the other source files a little bit leaner
 
 struct UpdateLevelMesh
 {
-	void SectorChanged(void *sector)
-	{
-	}
+	virtual void SectorChanged(void *sector) = 0;
 
-	void SideChanged(void *side)
-	{
-	}
+	virtual void SideChanged(void *side) = 0;
 };
 
-UpdateLevelMesh* LevelMeshUpdater;
+extern UpdateLevelMesh* LevelMeshUpdater;