fix(macOS): handle wallpaper detection without GUI

[niu541412]

On headless macOS, querying NSScreen connects to WindowServer and may abort. Check for a GUI session first, while keeping the plist and SQLite fallbacks available.

[CarterLi]

On headless macOS, querying NSScreen connects to WindowServer and may abort

What do you mean by abort? The entire displayserver_apple.c is talking to WindowServer. If connecting to WindowServer will abort the program it has been aborted in the Display module. No?

Not sure about the headless macOS either. The CI runner is a headless environment IMO and clearly has no real displays, but it can also have a virtual display.

https://github.com/fastfetch-cli/fastfetch/actions/runs/33584489343/job/100105891321

[niu541412]

This is probably due to the interface on older versions of macOS not handling this case properly.

---

fastfetch -s Wallpaper
_RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
2026-09-01 15:27:10.483 fastfetch[96727:71308553] *** Assertion failure in -[NSWorkspace desktopImageURLForScreen:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/AppKit/AppKit-1561.61.100/AppKit.subproj/NSWorkspace.m:2216
2026-09-01 15:27:10.484 fastfetch[96727:71308553] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid parameter not satisfying: screen != nil'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff37dcbf3b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x00007fff5f124942 objc_exception_throw + 48
2 CoreFoundation 0x00007fff37dd1b22 +[NSException raise:format:arguments:] + 98
3 Foundation 0x00007fff39f1a9f0 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 193
4 AppKit 0x00007fff35bc2041 -[NSWorkspace desktopImageURLForScreen:] + 380
5 fastfetch 0x000000010b727b71 ffDetectWallpaper + 100
6 fastfetch 0x000000010b6ff4c2 ffPrintWallpaper + 65
7 fastfetch 0x000000010b68ba09 ffPrintJsonConfig + 4670
8 fastfetch 0x000000010b67f997 main + 314
9 libdyld.dylib 0x00007fff5fd3f015 start + 1
10 ??? 0x0000000000000003 0x0 + 3
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Abort trap: 6

[CarterLi]

Please test 0286209