Fix problem when request did not have adequate arg in dhcp.pm

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/branches/2.8@16368 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd

xCAT-server/lib/xcat/plugins/dhcp.pm

@@ -1533,7 +1533,7 @@ sub process_request
             }
         }
 
-        @ARGV       = @{$req->{arg}};
+        if ($req && $req->{arg}) { @ARGV       = @{$req->{arg}}; } else { @ARGV=(); }
         $statements = "";
         GetOptions('s|statements=s' => \$statements);