flutter web : Unsupported operation: _Namespace

I'm using pdf package to generate pdf file and it works correctly on windows but get an exception when running on web (chrome).

Error: Unsupported operation: _Namespace
at Object.throw_ [as throw] (http://localhost:53375/dart_sdk.js:5333:11)
at Function.get _namespace [as _namespace] (http://localhost:53375/dart_sdk.js:55298:17)
at io._File.new.openSync (http://localhost:53375/dart_sdk.js:53257:45)
at io._File.new.readAsBytesSync (http://localhost:53375/dart_sdk.js:53320:25)
at get fontData (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:193763:58)
at Object.desc.get [as fontData] (http://localhost:53375/dart_sdk.js:5869:17)
at get data (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:193767:21)
at Object.desc.get [as data] (http://localhost:53375/dart_sdk.js:5869:17)
at get myFont (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:193771:35)
at Object.desc.get [as myFont] (http://localhost:53375/dart_sdk.js:5869:17)
at Function.buildSupplierAddress (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:187706:294)
at Function.buildHeader (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:187703:327)
at multi_page.MultiPage.new.<anonymous> (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:187698:134)
at multi_page.MultiPage.new.generate (http://localhost:53375/packages/pdf/src/widgets/table.dart.lib.js:16610:58)
at document$0.Document.new.addPage (http://localhost:53375/packages/pdf/src/widgets/table.dart.lib.js:18301:12)
at generate (http://localhost:53375/packages/reporting_system_admin/ui/Dashboard/PieChart/pie_chart_one_government.dart.lib.js:187698:13)
at generate.next (<anonymous>)
at http://localhost:53375/dart_sdk.js:39031:33
at _RootZone.runUnary (http://localhost:53375/dart_sdk.js:38888:58)
at _FutureListener.thenAwait.handleValue (http://localhost:53375/dart_sdk.js:33874:29)
at handleValueCallback (http://localhost:53375/dart_sdk.js:34434:49)
at Function._propagateToListeners (http://localhost:53375/dart_sdk.js:34472:17)
at _Future.new.[_completeWithValue] (http://localhost:53375/dart_sdk.js:34314:23)
at async._AsyncCallbackEntry.new.callback (http://localhost:53375/dart_sdk.js:34337:35)
at Object._microtaskLoop (http://localhost:53375/dart_sdk.js:39175:13)
at _startMicrotaskLoop (http://localhost:53375/dart_sdk.js:39181:13)
at http://localhost:53375/dart_sdk.js:34688:9

pdf api code :