library/RLCMAC_EncDec: fix segfault in encode_trailing_padding_spb()

Change-Id: Ib0992a50026f0e0deebb959788ed6e79c5286fec
Related: OS#6310
diff --git a/library/RLCMAC_EncDec.cc b/library/RLCMAC_EncDec.cc
index 1b56984..dd32d8f 100644
--- a/library/RLCMAC_EncDec.cc
+++ b/library/RLCMAC_EncDec.cc
@@ -455,6 +455,7 @@
 	if (data_len > blk_len_no_spb) {
 		fprintf(stderr, "Buffer too large for requested CS! %s (%s:%u)\n", __func__, __FILE__, __LINE__);
 		// TODO: throw exception?
+		return;
 	}
 
 	for (int i = 0; i < blk_len_no_spb - data_len; i++)