app: [Wayland] suppress spurious ConfigEvents

As reported By Larry Clapp, Wayland would send a ConfigEvent with
every FrameEvent when fallback client side decorations are enabled.
This is because Window would call the driver Option and Perform
methods even when they're empty.

The change applies to every platform, but was only observable on
Wayland.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/window.go

@@ -769,8 +769,12 @@ func (w *Window) decorate(e FrameEvent, o *op.Ops) image.Point {
 	}
 	// Update the window based on the actions on the decorations.
 	opts, acts := splitActions(deco.Update(gtx))
-	w.driver.Configure(opts)
-	w.driver.Perform(acts)
+	if len(opts) > 0 {
+		w.driver.Configure(opts)
+	}
+	if acts != 0 {
+		w.driver.Perform(acts)
+	}
 	style.Layout(gtx)
 	// Offset to place the frame content below the decorations.
 	decoHeight := gtx.Dp(w.decorations.Config.decoHeight)