BSSGP: properly print BVCI for signalling messages (BVCI=0)

Change-Id: I4ac0f48d2e62cd0545e8a1e1b26c9e43ef5e8dde
diff --git a/src/gprs_bssgp_pcu.cpp b/src/gprs_bssgp_pcu.cpp
index f99058a..dd9eb68 100644
--- a/src/gprs_bssgp_pcu.cpp
+++ b/src/gprs_bssgp_pcu.cpp
@@ -281,7 +281,7 @@
 	struct bssgp_normal_hdr *bgph = (struct bssgp_normal_hdr *) msgb_bssgph(msg);
 	enum bssgp_pdu_type pdu_type = (enum bssgp_pdu_type) bgph->pdu_type;
 	int rc = 0;
-	int bvci = bctx ? bctx->bvci : -1;
+	int bvci = bctx ? bctx->bvci : msgb_bvci(msg);
 	switch (pdu_type) {
 	case BSSGP_PDUT_STATUS:
 		/* already handled in libosmogb */