(insert_loc_no): Fixed a memory access error introduced in last commit.

src/server/membership.c

 /*
- * $Id: membership.c,v 0.73 2002/11/06 18:40:28 ceder Exp $
+ * $Id: membership.c,v 0.74 2002/11/06 19:46:17 ceder Exp $
  * Copyright (C) 1991-2002  Lysator Academic Computer Association.
  *
  * This file is part of the LysKOM server.
@@ -580,7 +580,7 @@ insert_loc_no(Local_text_no   text,
 
     if (text == lo->last_read + 1)
     {
-	if (lo != end && (lo+1)->first_read == text)
+	if (lo != end && lo + 1 != end && (lo+1)->first_read == text)
 	    return FAILURE;	/* This text was already read. */
 	lo->last_read = text;
 	return OK;