Fix NullPointerException in setupBroadcast when frameContainerLayout is null (Fixes #274)

[ricardosohn]

Hello,
I have tested the change proposed on #274 to resolve this issue and it worked.
Let me know if anything else is needed in this PR.
From the bug description itself:

Describe the bug
NullPointerException for Android when "toBack" is set to true.

NullPointerException: Attempt to invoke virtual method 'boolean android.widget.FrameLayout.dispatchTouchEvent(android.view.MotionEvent)' on a null object reference

To Reproduce
Steps to reproduce the behavior:

Integrate this plugin
Set "toBack" to true
Running app
When opening a screen that is invoking start of camera preview and user immediately clicks on screen when camera is not finished launching, app crashes
Expected behavior

App does not crash when clicking to early on screen..

Additional context

In the CameraPreview -> setupBroadcast method we invoke fragment.frameContainerLayout.dispatchTouchEvent(event);
This will crash when fragment.frameContainerLayout is null. This is not being checked accordingly. Please, check the current method below.

I think, there should be (null != fragment.frameContainerLayout) added to the if statement.

private void setupBroadcast() {
        /** When touch event is triggered, relay it to camera view if needed so it can support pinch zoom */

        getBridge().getWebView().setClickable(true);
        getBridge()
            .getWebView()
            .setOnTouchListener(
                new View.OnTouchListener() {
                    @Override
                    public boolean onTouch(View v, MotionEvent event) {
                        if ((null != fragment) && (fragment.toBack == true)) {
                            fragment.frameContainerLayout.dispatchTouchEvent(event);
                        }
                        return false;
                    }
                }
            );
    }