From Tim Moore, refactore WeakReference/Referenced to avoid signalling the observers when do a unref_nodelete.

include/osg/Referenced

@@ -89,8 +89,12 @@ class OSG_EXPORT Referenced
             not delete it, even if ref count goes to 0.  Warning, unref_nodelete() 
             should only be called if the user knows exactly who will
             be responsible for, one should prefer unref() over unref_nodelete() 
-            as the later can lead to memory leaks.*/
-        int unref_nodelete() const;
+            as the later can lead to memory leaks.
+
+            @param signalObserversOnZeroRefCount - By default true, adjust the reference count and send
+            any signal to observers if ref count goes to zero.
+        */
+        int unref_nodelete(bool signalObserversOnZeroRefCount = true) const;
         
         /** Return the number pointers currently referencing this object. */
         inline int referenceCount() const { return _refCount; }

include/osg/observer_ptr

@@ -47,7 +47,7 @@ struct WeakReference : public Observer, public Referenced
             // The object is in the process of being deleted, but our
             // objectDeleted() method hasn't been run yet (and we're
             // blocking it -- and the final destruction -- with our lock).
-            _ptr->unref_nodelete();
+            _ptr->unref_nodelete(false);
             return 0;
         }
         return _ptr;

src/osg/Referenced.cpp

@@ -334,7 +334,7 @@ void Referenced::setThreadSafeRefUnref(bool threadSafe)
 #endif
 }
 
-int Referenced::unref_nodelete() const
+int Referenced::unref_nodelete(bool signalObserversOnZeroRefCount) const
 {
     int result;
 #if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
@@ -355,7 +355,7 @@ int Referenced::unref_nodelete() const
     }
 #endif
 
-    if (needUnreferencedSignal)
+    if (needUnreferencedSignal && signalObserversOnZeroRefCount)
     {
         signalObserversAndDelete(true,false,false);
     }