don't trust Error_TYPE unless ErrorMessage is set

fix ^cstats fix


git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@401 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

C/cdmgr.c

@@ -866,7 +866,8 @@ addclause(Term t, CODEADDR cp, int mode, int mod)
     spy_flag = TRUE;
   if (mode == consult)
     not_was_reconsulted(p, t, TRUE);
-  if (Error_TYPE == PERMISSION_ERROR_MODIFY_STATIC_PROCEDURE)
+  /* always check if we have a valid error first */
+  if (ErrorMessage && Error_TYPE == PERMISSION_ERROR_MODIFY_STATIC_PROCEDURE)
     return;
   if (!is_dynamic(p)) {
     Clause     *clp = ClauseCodeToClause(cp);