Added an assert to the ValueIter constructor to check if the Node ptr is valid

Signed-off-by: Nick Avramoussis <[email protected]>

Author: Idclip

openvdb/openvdb/tree/LeafNode.h

@@ -229,7 +229,7 @@ class LeafNode
             // Unlike other value iterators, cache the buffer data as part of
             // the iterators members to avoid the cost of going through the
             // leaf buffer atomic/checking API
-            , mData(parent->buffer().data()) {}
+            , mData([&]() { OPENVDB_ASSERT(parent); return parent->buffer().data(); }()) {}
 
         ValueT& getItem(Index pos) const { return mData[pos]; }
         ValueT& getValue() const { return this->getItem(this->pos()); }