Fix reference counting in base objects and crash in NiNode for some Nif files.

Ref.h

@@ -38,7 +38,12 @@ protected:
 };
 
 template <class T>
-Ref<T>::Ref( T * object ) : _object(object) {}
+Ref<T>::Ref( T * object ) : _object(object) {
+   //If object isn't null, increment reference count
+   if ( _object != NULL ) {
+      _object->AddRef();
+   }
+}
 
 template <class T>
 Ref<T>::Ref(const Ref & ref_to_copy ) {

obj/NiNode.cpp

@@ -70,7 +70,7 @@ void NiNode::RemoveChild( Ref<NiAVObject> obj ) {
 
 void NiNode::ClearChildren() {
 	for ( vector< NiAVObjectRef >::iterator it = children.begin(); it != children.end(); ++it) {
-		(*it)->SetParent(NULL);
+      if (*it) (*it)->SetParent(NULL);
 	}
 	children.clear();
 }

obj/NiObject.cpp

@@ -33,9 +33,7 @@ void NiObject::AddRef() {
 }
 
 void NiObject::SubtractRef() {
-	--_ref_count;
-
-	if ( _ref_count < 0 ) {
+	if ( --_ref_count == 0 ) {
 		delete this;
 	}
 }

obj/NiObject.h

@@ -151,7 +151,7 @@ template <class T> Ref<T> StaticCast( NiObject * object ) {
 	return (T*)object;
 }
 
-template <class T> const Ref<T> SaticCast (const NiObject * object) {
+template <class T> Ref<const T> StaticCast (const NiObject * object) {
 	return (const T*)object;
 }
 
@@ -163,7 +163,7 @@ template <class T> Ref<T> DynamicCast( NiObject * object ) {
 	}
 }
 
-template <class T> const Ref<T> DynamicCast( const NiObject * object ) {
+template <class T> Ref<const T> DynamicCast( const NiObject * object ) {
 	if ( object->IsDerivedType(T::TYPE) ) {
 		return (const T*)object;
 	} else {