[tex-live] Bug in pdftex. Suggestions on who to report?

[Enrico Gregorio]

The following example, compiled with pdftex,

\edef\tenitnumber{\pdffontobjnum\tenit}
\message{The font number is \tenitnumber}

\tenitnumber

\bye

fails with

This is pdfTeX, Version 3.14159265-2.6-1.40.18 (TeX Live 2017) (preloaded format=pdftex)

 restricted \write18 enabled.
entering extended mode

(./alfon.tex{/usr/local/texlive/2017/texmf-var/fonts/map/pdftex/updmap/pdftex.m
ap} The font number is 1 [1]Assertion failed: (fo->last_char >= fo->first_char), function create_fontdictionary, file ../../../texk/web2c/pdftexdir/writefont.c, line 607.
 )Abort trap: 6

The similar 

\edef\first{\pdffeedback fontobjnum\tenit}

\first

\bye

doesn’t fail on LuaTeX.

Tested both on Mac OS X and Windows (Joseph Wright tested it).

Any suggestion on who to report the bug?

Ciao
Enrico