fix NoSuchMethodError on iOS(cordova)

[Error] NoSuchMethodError : method not found: 'Symbol("main")'
Receiver: ""
Arguments: []
	O9 (index.html_bootstrap.dart.precompiled.js, line 1424)
	(anonymous function) (index.html_bootstrap.dart.precompiled.js, line 2053)
	vV (index.html_bootstrap.dart.precompiled.js, line 718)
	Rq (index.html_bootstrap.dart.precompiled.js, line 494)
	(anonymous function) (index.html_bootstrap.dart.precompiled.js, line 10449)
	(anonymous function) (index.html_bootstrap.dart.precompiled.js, line 10449)
	(anonymous function) (index.html_bootstrap.dart.precompiled.js, line 10446)
	(anonymous function) (index.html_bootstrap.dart.precompiled.js, line 10448)