[fixed] fix pitfall when using == and != with MangedWeakReference

The following steps should illustrate the problem:

1. Object A is freshly constructed and gets an _objectID of 0.
2. ManagedWeakReference of A is created -> savedObjectID will be also 0
3. ObjectManager::persist is called and A gets a validi _objectID
4. ManagedWeakReference of A will still have the savedObjectID of 0
   and will result in wrong behaviour of == and !=

To circumvent these this commit changes the case when one of the
compared ManagedWeakReference instances has a savedObjectID of 0 and
checks the actual reference object for the real _objectID.

MMOEngine/src/engine/core/ManagedWeakReference.h

@@ -102,6 +102,12 @@ namespace engine {
 			return ref;
 		}
 
+		inline O getReferenceUnsafeNoReload() const {
+			O ref = WeakReference<O>::getReferenceUnsafeStaticCast();
+
+			return ref;
+		}
+
 		inline O getReferenceUnsafe() {
 			O ref = WeakReference<O>::getReferenceUnsafeStaticCast();
 
@@ -143,14 +149,47 @@ namespace engine {
 
 		inline bool operator!=(const ManagedWeakReference<O>& r) const {
 			auto savedObjectID = this->savedObjectID.load(std::memory_order_relaxed);
-
-			return savedObjectID != r.savedObjectID.load(std::memory_order_relaxed);
+			auto rSavedObjectID = r.savedObjectID.load(std::memory_order_relaxed);
+
+			// the savedObjectID may be incorrectly be 0
+			// if object O was given an objectID after
+			// creating the ManagedWeakReference - so we
+			// have to check for the actual objectID of O
+			// here
+			if (savedObjectID == 0 || rSavedObjectID == 0) {
+				O ref = getReferenceUnsafeNoReload();
+				O rRef = r.getReferenceUnsafeNoReload();
+
+				// if both are nullptr only the savedObjectIDs matter
+				if (ref == nullptr && rRef == nullptr)
+					return savedObjectID != rSavedObjectID;
+				// if one of them is null they can't be equal
+				else if (ref == nullptr || rRef == nullptr)
+					return true;
+				// if both are not null we can check the real object id
+				else
+					return ref->_getObjectID() != rRef->getObjectID();
+			} else
+				return savedObjectID != rSavedObjectID;
 		}
 
 		inline bool operator==(const ManagedWeakReference<O>& r) const {
 			auto savedObjectID = this->savedObjectID.load(std::memory_order_relaxed);
+			auto rSavedObjectID = r.savedObjectID.load(std::memory_order_relaxed);
+
+			// see comment on same logic in the operator!= code
+			if (savedObjectID == 0 || rSavedObjectID == 0) {
+				O ref = getReferenceUnsafeNoReload();
+				O rRef = r.getReferenceUnsafeNoReload();
 
-			return savedObjectID == r.savedObjectID.load(std::memory_order_relaxed);;
+				if (ref == nullptr && rRef == nullptr)
+					return savedObjectID == rSavedObjectID;
+				else if (ref == nullptr || rRef == nullptr)
+					return false;
+				else
+					return ref->_getObjectID() == rRef->getObjectID();
+			} else
+				return savedObjectID == rSavedObjectID;
 		}
 
 		inline ManagedReference<O> get() {