liblzma: Fix a memory leak in error path of lzma_index_dup().

lzma_index_dup() calls index_dup_stream() which, in case of
an error, calls index_stream_end() to free memory allocated
by index_stream_init(). However, it illogically didn't
actually free the memory. To make it logical, the tree
handling code was modified a bit in addition to changing
index_stream_end().

Thanks to Evan Nemerson for the bug report.

src/liblzma/common/index.c

@@ -202,5 +202,4 @@
 	if (node->right != NULL)
 		index_tree_node_end(node->right, allocator, free_func);
 
-	if (free_func != NULL)
 	free_func(node, allocator);
@@ -206,7 +205,5 @@
 	free_func(node, allocator);
-
-	lzma_free(node, allocator);
 	return;
 }
 
 
@@ -209,12 +206,12 @@
 	return;
 }
 
 
-/// Free the meory allocated for a tree. If free_func is not NULL,
-/// it is called on each node before freeing the node. This is used
-/// to free the Record groups from each index_stream before freeing
-/// the index_stream itself.
+/// Free the memory allocated for a tree. Each node is freed using the
+/// given free_func which is either &lzma_free or &index_stream_end.
+/// The latter is used to free the Record groups from each index_stream
+/// before freeing the index_stream itself.
 static void
 index_tree_end(index_tree *tree, const lzma_allocator *allocator,
 		void (*free_func)(void *node, const lzma_allocator *allocator))
 {
@@ -217,7 +214,9 @@
 static void
 index_tree_end(index_tree *tree, const lzma_allocator *allocator,
 		void (*free_func)(void *node, const lzma_allocator *allocator))
 {
+	assert(free_func != NULL);
+
 	if (tree->root != NULL)
 		index_tree_node_end(tree->root, allocator, free_func);
 
@@ -371,7 +370,8 @@
 index_stream_end(void *node, const lzma_allocator *allocator)
 {
 	index_stream *s = node;
-	index_tree_end(&s->groups, allocator, NULL);
+	index_tree_end(&s->groups, allocator, &lzma_free);
+	lzma_free(s, allocator);
 	return;
 }