cbor_encoder_create_array() returns CborErrorOutOfMemory (0x80000000)

Hi,
the code bellow causes that cbor_encoder_create_array returns CborErrorOutOfMemory.
```c
CborEncoder enc, array_enc;
u8_t buf[16];
cbor_encoder_init(&enc, buf, sizeof(buf), 0);
int res = 0;
res = cbor_encoder_create_array(&enc, &array_enc, 1);
```
How to create a CBOR array? Can you point me to some example. Thank you!