fix compiler warnings.

test/unit/utglTF2ImportExport.cpp

@@ -379,8 +379,9 @@ TEST_F(utglTF2ImportExport, importglTF2FromMemory) {
 TEST_F( utglTF2ImportExport, bug_import_simple_skin ) {
     Assimp::Importer importer;
     const aiScene *scene = importer.ReadFile( ASSIMP_TEST_MODELS_DIR "/glTF2/simple_skin/simple_skin.gltf", aiProcess_ValidateDataStructure );
-
+    EXPECT_NE( nullptr, scene );
 }
+
 #ifndef ASSIMP_BUILD_NO_EXPORT
 TEST_F( utglTF2ImportExport, exportglTF2FromFileTest ) {
     EXPECT_TRUE( exporterTest() );