Will topic isn't truncated when using a mount_point.

ChangeLog.txt

@@ -7,6 +7,7 @@ Broker:
   Closes #476314.
 - Reconnecting client with clean session set to false doesn't start with mid=1
   again.
+- Will topic isn't truncated by one byte when using a mount_point any more.
 
 Client library:
 - Fix the case where a message received just before the keepalive timer

src/read_handle_server.c

@@ -243,7 +243,7 @@ int mqtt3_handle_connect(struct mosquitto_db *db, struct mosquitto *context)
 		}
 
 		if(context->listener && context->listener->mount_point){
-			slen = strlen(context->listener->mount_point) + strlen(will_topic);
+			slen = strlen(context->listener->mount_point) + strlen(will_topic) + 1;
 			will_topic_mount = _mosquitto_malloc(slen+1);
 			if(!will_topic_mount){
 				rc = MOSQ_ERR_NOMEM;