[ic] Strange ic behavior with png image usertag created

[marco]

With Variable DEBUG 1 in main configuration file interchange.cfg all 
goes well but without DEBUG apache (not ic) give this error:

[Sat Dec 09 20:26:35.274482 2017] [http:error] [pid 680] [client 
192.168.11.2:58795] AH02429: Response header name 'libpng warning' 
contains invalid characters, aborting request,
  referer: 
https://newweb.omnib.it/cgi-bin/elcat/stat_ass.html?giorno=09&mese=11&anno=2016&giorno2=09&mese2=12&anno2=2016&min=&max=&cod_cli=&cli_order=des_cli&cod_resp=&da_chiamata=

Searching for this issue I have find this apache page:
https://blog.tigertech.net/posts/apache-cve-2016-8743/
that give responsability to malformed http header.

my enviro:
- Debian GNU/Linux 9
- Interchange V5.10.0
- perl 5.24.1

Attached usertag that create the image.

Any suggestions ?

-- 
"Fino alla bara sinpara"
"Up to demise we rize"
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