NSInternalInconsistencyException in WPMediaPickerViewController: threading violation: expected the main thread

[loremattei]

Sentry Url: https://sentry.io/share/issue/908f4cc518554171b60e5b272f81d555/
User Count: 99
Count: 359
First Release: 13.4.1.1
First Seen: 2019-11-06T23:18:15Z
Last Release: 14.5.0.2
Last Seen: 2020-04-14T03:37:21Z
24 Hours: 3
30 Days: 88

Stacktrace:

NSInternalInconsistencyException: threading violation: expected the main thread
    at null.__exceptionPreprocess(null:null)
    at null.objc_exception_throw(null:null)
    at null.+[NSException raise:format:arguments:](null:null)
    at null.-[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:](null:null)
    at null.-[FBSSerialQueue assertOnQueue](null:null)
    at null.-[FBSSceneImpl updateClientSettings:withTransitionContext:](null:null)
    at null.-[FBSSceneImpl updateClientSettingsWithTransitionBlock:](null:null)
    at null.-[FBSScene(UIApp) updateUIClientSettingsWithTransitionBlock:](null:null)
    at null.-[UIScene _updateUIClientSettingsWithUITransitionBlock:](null:null)
    at null.-[_UISystemAppearanceManager updateWhitePointAdaptivityStyle](null:null)
...
(21 additional frame(s) were not displayed)

[yaelirub]

Add DispatchQueue.main.async before calling [self.internalNavigationController pushViewController:viewController animated:YES]; in - (void)showAfterViewController:(UIViewController *)viewController

@leandroalonso , would you mind adding this when you're looking into #349 ?