Return {error, enonmem} in OOM situations

c_src/index.c

@@ -19,7 +19,7 @@ geef_index_new(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 
 	index = enif_alloc_resource(geef_index_type, sizeof(geef_index));
 	if (!index)
-		return atoms.error;
+		return geef_oom(env);
 
 	if (git_index_new(&index->index) < 0)
 		return geef_error(env);
@@ -69,7 +69,7 @@ geef_index_write_tree(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
 		return geef_error(env);
 
 	if (geef_oid_bin(&bin, &id) < 0)
-		return atoms.error;
+		return geef_oom(env);
 
 	return enif_make_tuple2(env, atoms.ok, enif_make_binary(env, &bin));
 }