fix pixel ratio (flutter#37268)

Author: cfontas

shell/platform/fuchsia/flutter/flatland_platform_view.cc

@@ -75,14 +75,14 @@ void FlatlandPlatformView::OnGetLayout(
   view_logical_size_ = {static_cast<float>(info.logical_size().width),
                         static_cast<float>(info.logical_size().height)};
 
-  float pixel_ratio = 1.0f;
   if (info.has_device_pixel_ratio()) {
     // Flatland returns a Vec2 for DPR but both values should be identical.
     FML_DCHECK(info.device_pixel_ratio().x == info.device_pixel_ratio().y);
     view_pixel_ratio_ = info.device_pixel_ratio().x;
-    pixel_ratio = *view_pixel_ratio_;
   }
 
+  float pixel_ratio = view_pixel_ratio_ ? *view_pixel_ratio_ : 1.0f;
+
   SetViewportMetrics({
       pixel_ratio,  // device_pixel_ratio
       std::round(view_logical_size_.value()[0] *