strtr() expects parameter 1 to be string, array given in /var/www/vhosts/vvwaspiktest.nl/httpdocs/drupal/includes/common.inc on

My working site was moved to another provider.
I dropped the files in a directory "httpdocs/drupal/". Now I have to access my site by www.vvwaspiktest.nl/drupal instead of www.vvwaspiktest.nl That is not a big deal, but when accessing www.vvwaspiktest.nl/drupal I get the message:
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warning: strtr() expects parameter 1 to be string, array given in /var/www/vhosts/vvwaspiktest.nl/httpdocs/drupal/includes/common.inc on line 944.

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Now I really do not have a clue what to do about this. When I click the log in the site turns to another layout but when I log in as admin it returns to the expected layout and the warning is gone.

1. What can I do about this?

2. Or is it maybe that Drupal expects an anonymus user to visit www.vvwaspiktest.nl instead of www.vvwaspiktest.nl/drupal?

Well, the files were moved up one folder so now I look at www.vvwaspiktest.nl but still the same warning. So question 1 is still the one to be answered.

Thanks for any help.