[Bug] GCC nonnull and format-overflow in r.fill.stats

[wenzeslaus]

Describe the bug

Compilation of r.fill.stats complains about "argument 1 null where non-null expected" with -Wnonnull and -Wformat-overflow for an sprintf call in calculate_raster_mode.

To reproduce

Run compilation in the nix develop environment or with -Wformat-overflow= and/or -Wnonnull (using GCC v13?).

Expected behavior

No errors or warnings. Possibly warnings treated as errors in Nix build.

Screenshots

VERSION_NUMBER=8.5.0dev /home/vpetras/Projects/grass/code/grass/dist.x86_64-pc-linux-gnu/utils/g.html2man.py "/home/vpetras/Projects/grass/code/grass/dist.x86_64-pc-linux-gnu/docs/html/r.fill.stats.html" "/home/vpetras/Projects/grass/code/grass/dist.x86_64-pc-linux-gnu/docs/man/man1/r.fill.stats.1"
In file included from /nix/store/wlavaybjbzgllhq11lib6qgr7rm8imgp-glibc-2.39-52-dev/include/stdio.h:980,
                 from main.c:38:
In function 'sprintf',
    inlined from 'calculate_raster_mode' at main.c:1164:9:
/nix/store/wlavaybjbzgllhq11lib6qgr7rm8imgp-glibc-2.39-52-dev/include/bits/stdio2.h:30:10: warning: argument 1 null where non-null expected [-Wnonnull]
   30 |   return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   31 |                                   __glibc_objsize (__s), __fmt,
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   32 |                                   __va_arg_pack ());
      |                                   ~~~~~~~~~~~~~~~~~
/nix/store/wlavaybjbzgllhq11lib6qgr7rm8imgp-glibc-2.39-52-dev/include/bits/stdio2.h:30:10: note: in a call to built-in function '__builtin_sprintf'
/nix/store/wlavaybjbzgllhq11lib6qgr7rm8imgp-glibc-2.39-52-dev/include/bits/stdio2.h:30:10: warning: null destination pointer [-Wformat-overflow=]
rm r.fill.stats.tmp.html
make[4]: Leaving directory '/home/vpetras/Projects/grass/code/grass/raster/r.fill.stats'

System description

• Our nix develop environment on Ubuntu 22.04.
• gcc (GCC) 13.3.0 (2023)
• GRASS GIS 8.5.0dev 573d54a

Additional context

• [Bug] lib: GCC format-overflow in G_recursive_remove #4471