iOS 12.2 scroll hangs

Our app seems to have the scrolling hang on certain pages. In the CDVWKWebViewEngine.m file on the (void)handleStopScroll method when I change the last line from -

a) `[wkWebView evaluateJavaScript:@"window.IonicStopScroll.fire()" completionHandler:nil];`

To -

b) `[wkWebView evaluateJavaScript:@"window.IonicStopScroll.cancel()" completionHandler:nil];`

The scrolling then seems to work. I'm not sure if there is an issue with this section in the wk-plugin.js file -

```js
var stopScrollFunc = null;
var stopScroll = {
stop: function stop(callback) {
if (!stopScrollFunc) {
stopScrollFunc = callback;
stopScrollHandler.postMessage('');
}
},
fire: function fire() {
stopScrollFunc && stopScrollFunc();
stopScrollFunc = null;
},
cancel: function cancel() {
stopScrollFunc = null;
}
};

window.Ionic.StopScroll = stopScroll;
// deprecated
window.IonicStopScroll = stopScroll;
```