fixed: don't crash on missing core, warn instead

git-svn-id: https://opensg.vrsource.org/svn/trunk@2242 4683daeb-ad0f-0410-a623-93161e962ae5

Source/System/GraphOp/OSGSingleTypeGraphOp.inl

@@ -78,8 +78,18 @@ SingleTypeGraphOp<Type>::~SingleTypeGraphOp(void)
 template < class Type > inline
 Action::ResultE SingleTypeGraphOp<Type>::traverseEnter(Node *node)
 {
-    if(node->getCore()->getType().isDerivedFrom(Type::getClassType()))
+    NodeCore *core = node->getCore();
+
+    if(core != NULL && core->getType().isDerivedFrom(Type::getClassType()))
+    {
         travNodeEnter(node);
+    }
+    else if(core == NULL)
+    {
+        SWARNING << "SingleTypeGraphOp<>::traverseEnter: Core is NULL."
+                 << std::endl;
+    }
+
     return Action::Continue;
 }
 
@@ -88,8 +98,18 @@ Action::ResultE SingleTypeGraphOp<Type>::traverseLeave(
     Node *node, 
     Action::ResultE)
 {
-    if(node->getCore()->getType().isDerivedFrom(Type::getClassType()))
+    NodeCore *core = node->getCore();
+
+    if(core != NULL && core->getType().isDerivedFrom(Type::getClassType()))
+    {
         travNodeLeave(node);
+    }
+    else if(core == NULL)
+    {
+        SWARNING << "SingleTypeGraphOp<>::traverseLeave: Core is NULL."
+                 << std::endl;
+    }
+
     return Action::Continue;
 }