When selecting multiple times the same language documentation, one
got the following errors:
Use of uninitialized value $n in pattern match (m//) at
/usr/local/lib/AMC/perl/AMC-gui.pl line 4315.
Attempt to free unreferenced scalar: SV 0x811d965a0, Perl interpreter:
0x801c22000 at /usr/local/lib/AMC/perl/AMC-gui.pl line 4329.
Attempt to free unreferenced scalar: SV 0x811d965a0, Perl interpreter:
0x801c22000 at /usr/local/lib/perl5/site_perl/Gtk3.pm line 558.