Fix dtls-client.c

tests/dtls-client.c

diff --git a/tests/dtls-client.c b/tests/dtls-client.c
index 46a893a..1979721 100644
--- a/tests/dtls-client.c
+++ b/tests/dtls-client.c
@@ -135,6 +135,8 @@
 
     memcpy(result, psk_key, psk_key_length);
     return psk_key_length;
+  case DTLS_PSK_HINT:
+    return 0;
   default:
     dtls_warn("unsupported request type: %d\n", type);
   }