window.webkit.messageHandlers.cordova.postMessage issue

using ionic cordova application with angular, recently got this error after upgrading the web view version to 5.0.1

[Error] Unhandled Promise rejection: – "undefined is not an object (evaluating 'window.webkit.messageHandlers.cordova.postMessage')" – "; Zone:" – "" – "; Task:" – "Promise.then" – "; Value:" (2)
TypeError: undefined is not an object (evaluating 'window.webkit.messageHandlers.cordova.postMessage') — cordova.js:965
iOSExec — cordova.js:965
execProxy — cordova.js:994
(anonymous function) — mainHandle.js:397
(anonymous function) — storage.js:5
ZoneAwarePromise — polyfills-es2015.js:34327
get — storage.js:4
(anonymous function) — AppRate.js:185
(anonymous function) — AppRate.js:297
build — cordova.js:47
require — cordova.js:62
localRequire — cordova.js:43
(anonymous function) — cordova.js:1194
(anonymous function) — cordova.js:1122
f — cordova.js:675
(anonymous function) — cordova.js:827
(anonymous function) — cordova.js:1114
onScriptLoadingComplete — cordova.js:1862
scriptLoadedCallback — cordova.js:1879
(anonymous function) — cordova.js:1833
wrapFn — polyfills-es2015.js:34585
runTask — polyfills-es2015.js:33534
invokeTask — polyfills-es2015.js:33847
invokeTask — polyfills-es2015.js:34988
globalZoneAwareCallback — polyfills-es2015.js:35014
(anonymous function) (cordova.js:1413)
(anonymous function) (polyfills-es2015.js:34026)
handleUnhandledRejection (polyfills-es2015.js:34046)
(anonymous function) (polyfills-es2015.js:34040)
drainMicroTaskQueue (polyfills-es2015.js:33943)
invokeTask (polyfills-es2015.js:33851)
invokeTask (polyfills-es2015.js:34988)
globalZoneAwareCallback (polyfills-es2015.js:35014)
[Error] TypeError: undefined is not an object (evaluating 'window.webkit.messageHandlers.cordova.postMessage')
runTask (polyfills-es2015.js:33538)
invokeTask (polyfills-es2015.js:33847)
invokeTask (polyfills-es2015.js:34988)
globalZoneAwareCallback (polyfills-es2015.js:35014)