This message keep filling up my log.

[root@rnsv-19 fop2]# tail error.log -f
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.
Use of uninitialized value in concatenation (.) or string at script/fop2_server.pl line 6111.