Flutter web error

[JAYDARANIYA]

GradientText( "Demo Text", style: new TextStyle( fontSize: width * 0.18, fontWeight: FontWeight.bold, fontFamily: 'Piedra', letterSpacing: 5.0, ), gradient: LinearGradient( colors: [ Colors.deepPurple, Colors.deepOrange, Colors.pink, ], ), ),

when I use this code I am getting an error running on flutter web

`
The following UnimplementedError was thrown during a scheduler callback:
UnimplementedError

When the exception was thrown, this was the stack
throw_ (dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart:212:49))
pushShaderMask (lib/_engine/engine/html/scene_builder.dart:231:5))
addToScene (packages/flutter/src/rendering/layer.dart:1814:26))
[_addToSceneWithRetainedRendering] (packages/flutter/src/rendering/layer.dart:442:5))
addChildrenToScene (packages/flutter/src/rendering/layer.dart:1029:14))

`