apprt/gtk: make sure noop winproto never initializes

src/apprt/gtk/App.zig

@@ -373,6 +373,7 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
         &config,
     );
     errdefer winproto_app.deinit(core_app.alloc);
+    log.debug("windowing protocol={s}", .{@tagName(winproto_app)});
 
     // This just calls the `activate` signal but its part of the normal startup
     // routine so we just call it, but only if the config allows it (this allows

src/apprt/gtk/winproto.zig

@@ -40,7 +40,7 @@ pub const App = union(Protocol) {
             }
         }
 
-        return .none;
+        return .{ .none = .{} };
     }
 
     pub fn deinit(self: *App, alloc: Allocator) void {

src/apprt/gtk/winproto/noop.zig

@@ -13,7 +13,7 @@ pub const App = struct {
         _: [:0]const u8,
         _: *const Config,
     ) !?App {
-        return .{};
+        return null;
     }
 
     pub fn deinit(self: *App, alloc: Allocator) void {