-fix memory leak for 0==p->length

git-svn-id: https://gnunet.org/svn/gnunet@33714 140774ce-b5e7-0310-ab8b-a85725594a96
-fix use after free

git-svn-id: https://gnunet.org/svn/gnunet@33715 140774ce-b5e7-0310-ab8b-a85725594a96
-fix use of uninitialized memory

git-svn-id: https://gnunet.org/svn/gnunet@33716 140774ce-b5e7-0310-ab8b-a85725594a96