more web fixes

Author: goderbauer

lib/web_ui/lib/src/engine/canvas_pool.dart

@@ -1011,13 +1011,10 @@ class ContextStateHandle {
           context.translate(shaderBounds!.left, shaderBounds.top);
         }
       }
-    } else if (paint.color != null) {
+    } else {
       final String? colorString = colorValueToCssString(paint.color);
       fillStyle = colorString;
       strokeStyle = colorString;
-    } else {
-      fillStyle = '#000000';
-      strokeStyle = '#000000';
     }
 
     final ui.MaskFilter? maskFilter = paint.maskFilter;

lib/web_ui/lib/src/engine/html/dom_canvas.dart

@@ -257,8 +257,7 @@ DomHTMLElement buildDrawRectElement(
     ..transformOrigin = '0 0 0'
     ..transform = effectiveTransform;
 
-  String cssColor =
-      paint.color == null ? '#000000' : colorValueToCssString(paint.color)!;
+  String cssColor = colorValueToCssString(paint.color)!;
 
   if (paint.maskFilter != null) {
     final double sigma = paint.maskFilter!.webOnlySigma;
@@ -352,10 +351,8 @@ SVGSVGElement pathToSvgElement(SurfacePath path, SurfacePaintData paint) {
       svgPath.setAttribute('stroke-linecap', '${stringForStrokeCap(paint.strokeCap)}');
     }
     svgPath.setAttribute('fill', 'none');
-  } else if (paint.color != null) {
-    svgPath.setAttribute('fill', colorValueToCssString(paint.color)!);
   } else {
-    svgPath.setAttribute('fill', '#000000');
+    svgPath.setAttribute('fill', colorValueToCssString(paint.color)!);
   }
   if (path.fillType == ui.PathFillType.evenOdd) {
     svgPath.setAttribute('fill-rule', 'evenodd');

lib/web_ui/lib/src/engine/html/painting.dart

@@ -268,9 +268,7 @@ class SurfacePaintData {
       if (strokeJoin != null) {
         buffer.write('strokeJoin = $strokeJoin; ');
       }
-      if (color != null) {
-        buffer.write('color = ${colorToCssString(ui.Color(color))}; ');
-      }
+      buffer.write('color = ${colorToCssString(ui.Color(color))}; ');
       if (shader != null) {
         buffer.write('shader = $shader; ');
       }

lib/web_ui/lib/src/engine/semantics/semantics.dart

@@ -868,7 +868,6 @@ class SemanticsObject {
   void updateSelf(SemanticsNodeUpdate update) {
     // Update all field values and their corresponding dirty flags before
     // applying the updates to the DOM.
-    assert(update.flags != null);
     if (_flags != update.flags) {
       _flags = update.flags;
       _markFlagsDirty();
@@ -1613,12 +1612,7 @@ class EngineSemanticsOwner {
   /// the Web Engine.
   ///
   /// The default mode is [AccessibilityMode.unknown].
-  AccessibilityMode get mode => _mode;
-  set mode(AccessibilityMode value) {
-    _mode = value;
-  }
-
-  AccessibilityMode _mode = AccessibilityMode.unknown;
+  AccessibilityMode mode = AccessibilityMode.unknown;
 
   /// Currently used [GestureMode].
   ///