Init pkg->tags to NULL in pkg_init

[lnksz]

Bug

pkg_t pkg;
pkg_init_from_file(&next, "/tmp/some.ipk"); // This calls pkg_init() under the hood
// Use pkg here
pkg_deinit(&pkg); // ==> free(pkg->tags) freeing an uninitialized pointer

This is not surfacing if one uses the pkg_new() call, as the underlaying calloc() sets this to 0, which could be NULL, so the free is ok. But as the described method is also legit by the API and spares a possible memory leak, the init should be added.