#18 Apache Error when login

[Don]

Every time i login or logout with my account apache2 generates an entry in the error log containing:

[Mon May 09 01:17:11 2011] [error] [client 79.255.124.x] [Mon May 9 01:17:11 2011] index.cgi: Use of uninitialized value in concatenation (.) or string at src/modules/Chirpy/UI/WebApp/Administration.pm line 169., referer: http://www.x.de//index.cgi?action=login
[Mon May 09 01:20:13 2011] [error] [client 79.255.124.x] [Mon May 9 01:20:13 2011] index.cgi: Use of uninitialized value in concatenation (.) or string at src/modules/Chirpy/UI/WebApp/Administration.pm line 169., referer: http://www.x.de//index.cgi?
[Mon May 09 01:20:25 2011] [error] [client 79.255.124.x] [Mon May 9 01:20:25 2011] index.cgi: Use of uninitialized value in concatenation (.) or string at src/modules/Chirpy/UI/WebApp/Administration.pm line 169., referer: http://www.x.de//index.cgi?action=logout

Everything works fine, but it kinda bothers me.