Potential null pointer reference

[yangyangtiantianlonglong]

openssl/test/ectest.c

Lines 2724 to 2738 in 846975f

	if (!TEST_ptr(ctx = BN_CTX_new()))
	return 0;
	if (!TEST_ptr(group = EC_GROUP_new_by_curve_name(nid)))
	goto err;
	is_prime = EC_GROUP_get_field_type(group) == NID_X9_62_prime_field;
	#ifdef OPENSSL_NO_EC2M
	if (!is_prime) {
	ret = TEST_skip("binary curves not supported in this build");
	goto err;
	}
	#endif
	BN_CTX_start(ctx);

test/ectest.c:2728 and 2734 may cause BN_CTX_end() -->BN_STACK_pop() coredump.