RLCMAC: Fix unbound spb value in decoded egprs data blocks

That field is only present in Header Type 3 blocks.

Change-Id: Ie05576d7d7c18933dd9abcdc055cbfe1e4e54756
diff --git a/library/RLCMAC_EncDec.cc b/library/RLCMAC_EncDec.cc
index ac22def..97bd0be 100644
--- a/library/RLCMAC_EncDec.cc
+++ b/library/RLCMAC_EncDec.cc
@@ -545,6 +545,7 @@
 	ret_val.bsn2__offset() = egprs1->bsn2_lo << 7 | egprs1->bsn2_hi;
 	ret_val.pr() = egprs1->pr;
 	ret_val.cps() = egprs1->cps;
+	ret_val.spb() = OMIT_VALUE;
 
 	ttcn_buffer.increase_pos(sizeof(*egprs1));
 	return ret_val;
@@ -571,6 +572,7 @@
 	ret_val.bsn2__offset() = 0; /*TODO: mark optional and not set ? */
 	ret_val.pr() = egprs2->pr;
 	ret_val.cps() = egprs2->cps;
+	ret_val.spb() = OMIT_VALUE;
 
 	ttcn_buffer.increase_pos(sizeof(*egprs2));
 	return ret_val;