BUG#25743 If undo_buffer_size (for LG) greater than the inital shared memory (default 20M), ndbd nodes are crashed

storage/ndb/src/kernel/vm/Pool.hpp:
  Only when m_pool.seize() return true, the ptr.i and ptr.p is assigned the ri
  ght value, or else the parameter ptr should be "not touched"

storage/ndb/src/kernel/vm/Pool.hpp

@@ -307,8 +307,11 @@ RecordPool<T, P>::seize(Ptr<T> & ptr)
 {
   Ptr<void> tmp;
   bool ret = m_pool.seize(tmp);
-  ptr.i = tmp.i;
-  ptr.p = static_cast<T*>(tmp.p);
+  if(likely(ret))
+  {
+    ptr.i = tmp.i;
+    ptr.p = static_cast<T*>(tmp.p);
+  }
   return ret;
 }