Fix issues with child creation in BMessage nodes.

BMessageValueNode and BMessageFieldNode weren't correctly setting
the children created flag. This would result in duplicates of
some of the nodes showing up, especially in the case of nested messages.

src/apps/debugger/value/value_nodes/BMessageValueNode.cpp

@@ -330,9 +330,6 @@ BMessageValueNode::ResolvedLocationAndValue(ValueLoader* valueLoader,
 status_t
 BMessageValueNode::CreateChildren()
 {
-	if (!fChildren.IsEmpty())
-		return B_OK;
-
 	DataMember* member = NULL;
 	CompoundType* messageType = dynamic_cast<CompoundType*>(fType);
 	for (int32 i = 0; i < messageType->CountDataMembers(); i++) {
@@ -374,6 +371,8 @@ BMessageValueNode::CreateChildren()
 		fChildren.AddItem(node);
 	}
 
+	fChildrenCreated = true;
+
 	if (fContainer != NULL)
 		fContainer->NotifyValueNodeChildrenCreated(this);
 
@@ -656,6 +655,8 @@ BMessageValueNode::BMessageFieldNode::CreateChildren()
 		fChildren.AddItem(child);
 	}
 
+	fChildrenCreated = true;
+
 	if (fContainer != NULL)
 		fContainer->NotifyValueNodeChildrenCreated(this);