core: Fix "cat" crashing when it should have returned ENOENT

src/libostree/ostree-repo-file.c

@@ -992,6 +992,9 @@ ostree_repo_file_read (GFile         *file,
   OstreeRepoFile *self = OSTREE_REPO_FILE (file);
   const char *checksum;
 
+  if (!ostree_repo_file_ensure_resolved (self, error))
+    goto out;
+
   if (self->tree_contents)
     {
       g_set_error_literal (error, G_IO_ERROR,

src/ostree/ot-builtin-cat.c

@@ -41,9 +41,6 @@ cat_one_file (GFile         *f,
   gboolean ret = FALSE;
   GInputStream *in = NULL;
   
-  if (!ostree_repo_file_ensure_resolved ((OstreeRepoFile*)f, NULL))
-    g_assert_not_reached ();
-
   in = (GInputStream*)g_file_read (f, cancellable, error);
   if (!in)
     goto out;