[webconfig] fallback to default configs if https ones are not defined When cubicweb serves a request with an https scheme, it tries to access ``https_uiprops`` and ``https_datadir_urls``. However if those are not defined we should fallback to unsecure url instead of crashing with a traceback. There are very valid usecases for undefined https url. For example if your ``base_url``, ``datadir_url`` and uiprops content are already https urls. Closes #2786643

\.svn
^build$
^dist$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data/database/.*\.sqlite
.*/data/database/.*\.config
.*/data/database/tmpdb.*
.*/data/ldapdb/.*
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/