Fix: Prevent NPE when toBack=true and user taps before preview is ready (Android)

[ryaa]

Problem

When toBack=true, the plugin forwards WebView touch events to the native camera container to support pinch-to-zoom.
Previously, the WebView OnTouchListener was installed during startCamera(), before the CameraActivity fragment view was created.

Because FragmentTransaction.commit() is asynchronous, there is a short window where:

• fragment != null (fragment instance created)
• fragment.toBack == true (option applied)
• fragment.frameContainerLayout == null (initialized later in CameraActivity.onCreateView())

If the user tapped during that window, the touch-forwarding path called:

fragment.frameContainerLayout.dispatchTouchEvent(event);

…and crashed with:

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

Changes

This PR eliminates the race and adds defense-in-depth:

1) Install touch-forwarding only after the camera/fragment is ready

• Removed setupBroadcast() call from startCamera().
• Added setupBroadcast() in onCameraStarted() (before resolving the saved start call), ensuring the fragment view hierarchy exists and frameContainerLayout is initialized.

2) Add a null guard in the touch-forwarding path

Touch forwarding now checks:

• fragment != null
• fragment.toBack == true
• fragment.frameContainerLayout != null

If not ready, touch events are simply not forwarded (no crash).

3) Remove the WebView touch listener on stop

• stop() now clears the WebView touch listener via:
  • getBridge().getWebView().setOnTouchListener(null);

This prevents stale listeners from persisting across stop/start cycles or teardown.

Why this works

The listener is now installed only after CameraActivity has reached a state where its view is created and the camera preview is started, removing the timing window that previously allowed frameContainerLayout to be null.

Manual test checklist

• toBack=true: call startCamera() and tap immediately/repeatedly while the preview is launching → no crash
• toBack=true: once preview is visible, pinch-to-zoom still works
• Call stopCamera() and tap afterward → no crash, listener removed
• Repeat start → stop → start multiple times → stable, no listener leaks/crashes