nk_begin_titled/nk_font_atlas_add_from_file segfault

nk_font_atlas_add_from_file can induce a segfault in nk_begin_titled if the font file is not found.

Specifically here, ctx->style.font exists (but is invalid) so ctx->style.font->width causes segfault. (nk_begin_titled, about ~19965)

NK_ASSERT(ctx->style.font && ctx->style.font->width && "if this triggers you forgot to add a font");

You could probably solve this by checking &size (nk_font_atlas_add_from_file, about ~17303):
memory = nk_file_load(file_path, &size, &atlas->permanent);

Start with nk_font_atlas_add_from_file around the nk_file_load call near ~17303, then trace how its size result affects ctx->style.font in nk_begin_titled around ~19965. Reproduce the missing-font case and verify that it no longer reaches ctx->style.font->width with an invalid font; preserve the existing assertion for genuinely missing fonts.

Written by the indexing model from the issue text.