Tree/Trie: Check the end of buffer

We set buffer->pos to buffer->end in function buffer_print() when
bvsnprintf() failed, so there would be uninitialized memory between
the old buffer->pos and the current buffer->pos.

filter/tree.c

@@ -165,6 +165,9 @@ tree_format(struct f_tree *t, buffer *buf)
  
   tree_node_format(t, buf);
 
+  if (buf->pos == buf->end)
+    return;
+
   /* Undo last separator */
   if (buf->pos[-1] != '[')
     buf->pos -= 2;

filter/trie.c

@@ -300,6 +300,9 @@ trie_format(struct f_trie *t, buffer *buf)
     buffer_print(buf, "%I/%d, ", IPA_NONE, 0);
   trie_node_format(t->root, buf);
 
+  if (buf->pos == buf->end)
+    return;
+
   /* Undo last separator */
   if (buf->pos[-1] != '[')
     buf->pos -= 2;