Crash when loading fontconfig

[chrisduerr]

This has been reported to Alacritty in alacritty/alacritty#4591.

Generally the fontconfig of sctk should probably be reworked, but even if it doesn't it should under no circumstances just prevent the entire application from working. An unwrap in sctk on something that can actually occur seems rather inappropriate.

[elinorbgr]

Indeed, this whole block should be formulated in a more error-tolerant way:

client-toolkit/src/window/concept_frame.rs

Lines 642 to 648 in f038eab

	if let Some(font) = fontconfig::FontConfig::new()
	.unwrap()
	.get_regular_family_fonts(&font_face)
	.unwrap()
	.iter()
	.find(|p| p.extension().map(|e| e == "ttf").unwrap_or(false))
	{

Probably the behavior should be to just log a warning when failing to load fontconfig, and just don't display any text.

[brightly-salty]

I'd be willing to attempt to implement this and submit a PR if it would be accepted.

[elinorbgr]

@brightly-salty Thanks for offering your help, such a PR would be welcome ! :)