#6 TMPL_VAR default misbehaves on js or url es

[Mina Naguib]

If a TMPL_VAR has a DEFAULT set as well as ESCAPE set to either JS or
URL, then default value will be prepended to the variable's value even if it
is not empty.

This can be fixed by modifying line 2723 in HTML/Template.pm to:
*line = \$parse_stack[++$x] if grep {ref $line eq $_}
('HTML::Template::ESCAPE', 'HTML::Template::JSESCAPE',
'HTML::Template::URLESCAPE');