Addressed a number of memory leaks identified in unit tests by asan

test/unit/utSceneCombiner.cpp

@@ -42,6 +42,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include "UnitTestPCH.h"
 #include <assimp/SceneCombiner.h>
 #include <assimp/mesh.h>
+#include <memory>
 
 using namespace ::Assimp;
 
@@ -63,8 +64,10 @@ TEST_F( utSceneCombiner, MergeMeshes_ValidNames_Test ) {
     mesh3->mName.Set( "mesh_3" );
     merge_list.push_back( mesh3 );
 
-    aiMesh *out( nullptr );
-    SceneCombiner::MergeMeshes( &out, 0, merge_list.begin(), merge_list.end() );
+    std::unique_ptr<aiMesh> out;
+    aiMesh* ptr = nullptr;
+    SceneCombiner::MergeMeshes( &ptr, 0, merge_list.begin(), merge_list.end() );
+    out.reset(ptr);
     std::string outName = out->mName.C_Str();
     EXPECT_EQ( "mesh_1.mesh_2.mesh_3", outName );
 }