Freeciv

../../../src/common/mapimg.c: In function ‘mapimg_generate_name’:
../../../src/common/mapimg.c:1765:7: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
1765 | cat_snprintf(mapstr, sizeof(mapstr), "%s", mapimg_layer_name(layer)); | ^_~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This only started happening now in both Debian Bullseye and Sid after some system update. It also happens only with S2_5 though the code in question seem identical in later branches.