Fix ValueError exception when no disks are detected in the disk menu

in lib/disk/disk_menu.py, the menu items are created using info from a list called "devices" (device_handler.devices). when no block devices are detected, the list is empty, creating zero MenuItems, and causing the following ValueError:

ValueError: Menu must have at least one item

this change checks if the length of the list is shorter than 1  (empty list) before constructing the menu. if the list is empty, the user will be notified that no disks were detected. otherwise, the menu is created and behaves as normal

archinstall/lib/disk/disk_menu.py

@@ -311,6 +311,10 @@ async def select_devices(preset: list[BDevice] | None = []) -> list[BDevice] | N
 
 	devices = device_handler.devices
 
+	if len(devices) < 1:
+		await Notify(tr("No disks were detected. A disk is required to be able to install Arch Linux")).show()
+		return None
+	
 	items = [
 		MenuItem(
 			str(d.device_info.path),