Break out if language already selected is always true

First of all, thank you for this great extension!

I would like to report a little mistake, which has slipped in with the last release (8.1.0 ). It is located in the following line of the code:

https://git.spooner.io/spooner/rlmp_language_detection/blob/master/Classes/LanguageDetection.php#L87

GeneralUtility::_GP($this->conf['languageGPVar']) !== '' is TRUE even if there is no value given for the variable. So as far as I am concerned it should be changed to GeneralUtility::_GP($this->conf['languageGPVar']) != ''

The full condition would look like this:

if (!$this->conf['dontBreakIfLanguageIsAlreadySelected'] && (GeneralUtility::_GP($this->conf['languageGPVar']) !== null || GeneralUtility::_GP($this->conf['languageGPVar']) != '')) {