Check for session file name in autologin (closes #895)

Signed-off-by: AnErrupTion <anerruption@disroot.org>

src/Environment.zig

@@ -14,6 +14,7 @@ pub const DesktopEntry = struct {
 pub const Entry = struct { @"Desktop Entry": DesktopEntry = .{} };
 
 entry_ini: ?Ini(Entry) = null,
+file_name: []const u8 = "",
 name: []const u8 = "",
 xdg_session_desktop: ?[]const u8 = null,
 xdg_session_desktop_owned: bool = false,