libmsc/gsm_09_11.c: drop redundant assertion of stored msgb

It's already asserted at the beginning of handle_paging_event().

Change-Id: Ia558e11c6bde7bff130e4b76a4402ecc8068f1ed
diff --git a/src/libmsc/gsm_09_11.c b/src/libmsc/gsm_09_11.c
index b863ce8..63a1047 100644
--- a/src/libmsc/gsm_09_11.c
+++ b/src/libmsc/gsm_09_11.c
@@ -237,8 +237,6 @@
 
 		/* Send stored message */
 		ss_msg = transt->ss.msg;
-		OSMO_ASSERT(ss_msg);
-
 		gh = (struct gsm48_hdr *) msgb_push(ss_msg, sizeof(*gh));
 		gh->proto_discr  = GSM48_PDISC_NC_SS;
 		gh->proto_discr |= transt->transaction_id << 4;