Add missig docs and fix some small review findings.

code/ScenePrivate.h

@@ -42,22 +42,24 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 /** @file Stuff to deal with aiScene::mPrivate
  */
+#pragma once
 #ifndef AI_SCENEPRIVATE_H_INCLUDED
 #define AI_SCENEPRIVATE_H_INCLUDED
 
 #include <assimp/scene.h>
 
-namespace Assimp    {
+namespace Assimp {
 
+// Forward declarations
 class Importer;
 
 struct ScenePrivateData {
-
     ScenePrivateData()
-        : mOrigImporter()
-        , mPPStepsApplied()
-        , mIsCopy()
-    {}
+    : mOrigImporter( nullptr )
+    , mPPStepsApplied( 0 )
+    , mIsCopy( false ) {
+        // empty
+    }
 
     // Importer that originally loaded the scene though the C-API
     // If set, this object is owned by this private data instance.
@@ -75,14 +77,24 @@ struct ScenePrivateData {
 };
 
 // Access private data stored in the scene
-inline ScenePrivateData* ScenePriv(aiScene* in) {
+inline
+ScenePrivateData* ScenePriv(aiScene* in) {
+    ai_assert( nullptr != in );
+    if ( nullptr == in ) {
+        return nullptr;
+    }
     return static_cast<ScenePrivateData*>(in->mPrivate);
 }
 
-inline const ScenePrivateData* ScenePriv(const aiScene* in) {
+inline
+const ScenePrivateData* ScenePriv(const aiScene* in) {
+    ai_assert( nullptr != in );
+    if ( nullptr == in ) {
+        return nullptr;
+    }
     return static_cast<const ScenePrivateData*>(in->mPrivate);
 }
 
-}
+} // Namespace Assimp
 
-#endif
+#endif // AI_SCENEPRIVATE_H_INCLUDED