ui-tree: free read_sha1_file() buffer after use

Free up the buffer allocated in read_sha1_file()

Signed-off-by: Andy Green <andy@warmcat.com>
Signed-off-by: John Keeping <john@keeping.me.uk>
diff --git a/ui-tree.c b/ui-tree.c
index 67fd1bc..524de0f 100644
--- a/ui-tree.c
+++ b/ui-tree.c
@@ -127,6 +127,8 @@
 		print_binary_buffer(buf, size);
 	else
 		print_text_buffer(basename, buf, size);
+
+	free(buf);
 }
 
 struct single_tree_ctx {