[AC-6674] Android: Accessing WebView's requestHeaders property failing urls to load

A simple accidental test led me to this bug that: - Accessing *requestHeaders* property of WebView before the window is opened is stopping urls to load. - Once window is opened, we can access or set *requestHeaders* property without any issue. Though in the docs, it's mentioned to set *requestHeaders* property only in *createWebView* method or in *open* event, but not sure how it is related to simply accessing the property just for printing purpose. Attached screenshots are enough to show the behaviour of the issue. - Screenshot 1.JPG shows empty web-view as we are accessing the *requestHeaders* property before window is opened. - Screenshot 2.JPG shows loaded web-view if we access *requestHeaders* after window is opened.