An error occurs when the config parameter is not set.
Because the editor tried to initiate with the config file when params.config is 'undefined', because 'undefined' is not empty string.

This bug was added in https://github.com/pubannotation/textae/commit/6fd2593bdbea07e2acd9ee5382f042244bd6dc14
Merge pull request #86 from pubannotation/bugfix_error_without_config

An error occurs when the config parameter is not set.