Add decoding empty buffer test calls for cipher modes that benefit from this
diff --git a/tests/suites/test_suite_cipher.arc4.data b/tests/suites/test_suite_cipher.arc4.data
index 6e69b81..d29d2ae 100644
--- a/tests/suites/test_suite_cipher.arc4.data
+++ b/tests/suites/test_suite_cipher.arc4.data
@@ -1,3 +1,7 @@
+ARC4 Decrypt empty buffer
+depends_on:MBEDTLS_ARC4_C
+dec_empty_buf:MBEDTLS_CIPHER_ARC4_128
+
 ARC4 Encrypt and decrypt 0 bytes
 depends_on:MBEDTLS_ARC4_C
 enc_dec_buf:MBEDTLS_CIPHER_ARC4_128:"ARC4-128":128:0:-1