Pass paging group instead of imsi where later is not needed

Change-Id: Id0663a81f439f2d0b893b0d34f85a6db1927ef8e
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 389b186..61d8d58 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -803,6 +803,7 @@
 
 void gprs_rlcmac_tbf::poll_timeout()
 {
+	uint16_t pgroup;
 	gprs_rlcmac_ul_tbf *ul_tbf = as_ul_tbf(this);
 
 	LOGPTBF(this, LOGL_NOTICE, "poll timeout for FN=%d, TS=%d (curr FN %d)\n",
@@ -902,7 +903,9 @@
 			LOGPTBF(dl_tbf, LOGL_DEBUG, "Re-send dowlink assignment on PCH (IMSI=%s)\n",
 				imsi());
 			/* send immediate assignment */
-			dl_tbf->bts->snd_dl_ass(dl_tbf, false, imsi());
+			if ((pgroup = imsi2paging_group(imsi())) > 999)
+				LOGPTBF(dl_tbf, LOGL_ERROR, "IMSI to paging group failed! (%s)\n", imsi());
+			dl_tbf->bts->snd_dl_ass(dl_tbf, false, pgroup);
 			dl_tbf->m_wait_confirm = 1;
 		}
 	} else