MainActivity: refresh epdRootView in surfaceCreated

Ensures the cached root view is always fresh when the surface is
(re)created, rather than relying solely on the onCreate assignment.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: backcountrymountains

app/src/main/java/org/koreader/launcher/MainActivity.kt

@@ -172,6 +172,7 @@ class MainActivity : NativeActivity(), LuaInterface,
 
     override fun surfaceCreated(holder: SurfaceHolder) {
         super.surfaceCreated(holder)
+        epdRootView = view ?: window.decorView.rootView
         drawSplashScreen(holder)
     }