If there are no uncached tracks, don't spawn child processes to handle empty requests. The parent process code isn't expecting to wait for the children in this case, which, using Perl 5.18.4 running under mod_fcgid 2.3.9 on Apache 2.2.29, would apparently result in the FastCGI process terminating after issuing the error:
SIGCHLD received, but no signal handler set.
[Tue May 12 15:43:25 2015] [warn] [client 192.168.0.1] mod_fcgid: error reading data, FastCGI server closed connection, referer: http://soybase.org/gb2/gbrowse/gmax1.01/
If there are no uncached tracks, don't spawn child processes to handle empty requests. The parent process code isn't expecting to wait for the children in this case, which, using Perl 5.18.4 running under mod_fcgid 2.3.9 on Apache 2.2.29, would apparently result in the FastCGI process terminating after issuing the error: