Etherpad crash if a padID contains a special dash "–"

[zamentur]

Etherpad crash if a padID contains a special dash "–" and if we call the markdown export route.

The error:

2020-06-23 01:23:37.732] [ERROR] console - TypeError [ERR_INVALID_CHAR]: Invalid character in header content ["Content-disposition"]
    at ServerResponse.setHeader (_http_outgoing.js:473:3)
    at /var/www/etherpad_mypads/node_modules/ep_markdown/express.js:10:11
    at /var/www/etherpad_mypads/node_modules/ep_markdown/exportMarkdown.js:427:5
    at /var/www/etherpad_mypads/node_modules/ep_markdown/exportMarkdown.js:59:5
    at /var/www/etherpad_mypads/node_modules/ep_markdown/exportMarkdown.js:52:5
    at fn (/var/www/etherpad_mypads/src/node_modules/async/lib/async.js:641:34)
    at Immediate.<anonymous> (/var/www/etherpad_mypads/src/node_modules/async/lib/async.js:557:34)
    at runCallback (timers.js:705:18)
    at tryOnImmediate (timers.js:676:5)
    at processImmediate (timers.js:658:5)

Could be temporary fixed with try except.