BGE: Fix T40555: LibLoad material caching issue

Previously we don't merge material cached list, it create dangling pointer and memory leak.
Now we merge material cache list during the scene merge, and remove material in this list during the library free.

Reviewers: agoose77, dfelinto, hg1, pgi, campbellbarton, moguri

Reviewed By: campbellbarton, moguri

Subscribers: campbellbarton, youle, kupoman

Projects: #game_engine

Differential Revision: https://developer.blender.org/D1278

source/gameengine/Converter/KX_BlenderSceneConverter.cpp

@@ -1218,6 +1218,8 @@ bool KX_BlenderSceneConverter::FreeBlendFile(Main *maggie)
 		bmat = bl_mat->GetBlenderMaterial();
 
 		if (IS_TAGGED(bmat)) {
+			// Remove the poly material coresponding to this Blender Material.
+			m_polymat_cache[polymit->first].erase(bmat);
 			delete (*polymit).second;
 			*polymit = m_polymaterials.back();
 			m_polymaterials.pop_back();
@@ -1233,6 +1235,8 @@ bool KX_BlenderSceneConverter::FreeBlendFile(Main *maggie)
 	for (i = 0, matit = m_materials.begin(); i < size; ) {
 		BL_Material *mat = (*matit).second;
 		if (IS_TAGGED(mat->material)) {
+			// Remove the bl material coresponding to this Blender Material.
+			m_mat_cache[matit->first].erase(mat->material);
 			delete (*matit).second;
 			*matit = m_materials.back();
 			m_materials.pop_back();
@@ -1354,6 +1358,16 @@ bool KX_BlenderSceneConverter::MergeScene(KX_Scene *to, KX_Scene *from)
 		}
 	}
 
+	MaterialCache::iterator matcacheit = m_mat_cache.find(from);
+	// Merge cached BL_Material map.
+	m_mat_cache[to].insert(matcacheit->second.begin(), matcacheit->second.end());
+	m_mat_cache.erase(matcacheit);
+
+	PolyMaterialCache::iterator polymatcacheit = m_polymat_cache.find(from);
+	// Merge cached RAS_IPolyMaterial map.
+	m_polymat_cache[to].insert(polymatcacheit->second.begin(), polymatcacheit->second.end());
+	m_polymat_cache.erase(polymatcacheit);
+
 	return true;
 }