Fix the flexible space bar to still create a rendering object even if… (#62690)

packages/flutter/lib/src/material/flexible_space_bar.dart

@@ -303,7 +303,6 @@ class _FlexibleSpaceBarState extends State<FlexibleSpaceBar> {
           const double fadeEnd = 1.0;
           assert(fadeStart <= fadeEnd);
           final double opacity = 1.0 - Interval(fadeStart, fadeEnd).transform(t);
-          if (opacity > 0.0) {
           double height = settings.maxExtent;
 
           // StretchMode.zoomBackground
@@ -311,13 +310,15 @@ class _FlexibleSpaceBarState extends State<FlexibleSpaceBar> {
             constraints.maxHeight > height) {
             height = constraints.maxHeight;
           }
-
           children.add(Positioned(
             top: _getCollapsePadding(t, settings),
             left: 0.0,
             right: 0.0,
             height: height,
             child: Opacity(
+              // IOS is relying on this semantics node to correctly traverse
+              // through the app bar when it is collapsed.
+              alwaysIncludeSemantics: true,
               opacity: opacity,
               child: widget.background,
             ),
@@ -340,7 +341,6 @@ class _FlexibleSpaceBarState extends State<FlexibleSpaceBar> {
             ));
           }
         }
-        }
 
         // title
         if (widget.title != null) {