Fixed small issue with old trigger run when no old triggers

line 9554

bin/pt-online-schema-change

@@ -9551,11 +9551,13 @@ sub main {
       print "Adding original triggers to new table.\n";
 
       foreach my $orig_trigger (@orig_triggers) {
+         if ($orig_trigger ne '') {
             PTDEBUG && _d($orig_trigger);
             print $orig_trigger, "\n" if $o->get('print');
             $cxn->dbh()->do($orig_trigger);
          }
       }
+   }
 
    my $old_tbl;
    if ( $o->get('swap-tables') ) {