--- /tmp/02092018/asterisk-15.5.0/channels/chan_sip.c	2018-07-12 18:36:50.000000000 +0200
+++ chan_sip.c	2018-09-03 14:20:36.000000000 +0200
@@ -2574,12 +2574,15 @@
 	}
 
 	ao2_lock(tcptls_session);
-
-	if (!(th = ao2_t_find(threadt, &tmp, OBJ_POINTER, "ao2_find, getting sip_threadinfo in tcp helper thread")) ||
+	
+	// check stream isn't NULL
+	if (    (!tcptls_session->stream) ||
+		!(th = ao2_t_find(threadt, &tmp, OBJ_POINTER, "ao2_find, getting sip_threadinfo in tcp helper thread")) ||
 		!(packet = ao2_alloc(sizeof(*packet), tcptls_packet_destructor)) ||
 		!(packet->data = ast_str_create(len))) {
 		goto tcptls_write_setup_error;
 	}
+	
 
 	/* goto tcptls_write_error should _NOT_ be used beyond this point */
 	ast_str_set(&packet->data, 0, "%s", (char *) buf);
@@ -3097,7 +3100,7 @@
 
 			if (read(me->alert_pipe[0], &alert, sizeof(alert)) == -1) {
 				ast_log(LOG_ERROR, "read() failed: %s\n", strerror(errno));
-				continue;
+				goto cleanup; // read failed, usually Bad file descriptor, so go to cleanup to be safe
 			}
 
 			switch (alert) {
@@ -3116,9 +3119,11 @@
 					}
 					ao2_t_ref(packet, -1, "tcptls packet sent, this is no longer needed");
 				}
+				else goto cleanup; //frame_q is empty, nothing to write, go to cleanup to be safe
 				break;
 			default:
 				ast_log(LOG_ERROR, "Unknown tcptls thread alert '%u'\n", alert);
+				goto cleanup; // weird things, go to cleanup to be safe
 			}
 		}
 	}