Warn about invalid arguments to ColorFilter.mode (flutter#32269)

Author: jason-simmons

lib/web_ui/lib/src/engine/canvaskit/canvaskit_api.dart

@@ -970,7 +970,7 @@ class SkMaskFilter {
 
 @JS()
 class SkColorFilterNamespace {
-  external SkColorFilter MakeBlend(Float32List color, SkBlendMode blendMode);
+  external SkColorFilter? MakeBlend(Float32List color, SkBlendMode blendMode);
   external SkColorFilter MakeMatrix(
     Float32List matrix, // 20-element matrix
   );

lib/web_ui/lib/src/engine/canvaskit/color_filter.dart

@@ -83,10 +83,14 @@ class CkBlendModeColorFilter extends CkColorFilter {
 
   @override
   SkColorFilter _initRawColorFilter() {
-    return canvasKit.ColorFilter.MakeBlend(
+    final SkColorFilter? filter = canvasKit.ColorFilter.MakeBlend(
       toSharedSkColor1(color),
       toSkBlendMode(blendMode),
     );
+    if (filter == null) {
+      throw ArgumentError('Invalid parameters for blend mode ColorFilter');
+    }
+    return filter;
   }
 
   @override