Fix "double install" caused by config changes

Configuration changes in FlashFragment may cause the installation process to be triggered twice. The simplest way to reproduce this behavior is to choose a module ZIP file in landscape mode (which is the default on some tablets).

This commit fixes the problem by ensuring `savedInstanceState == null` before starting installation.

app/src/main/java/com/topjohnwu/magisk/ui/flash/FlashFragment.kt

@@ -51,8 +51,10 @@ class FlashFragment : BaseFragment<FragmentFlashMd2Binding>() {
 
         defaultOrientation = activity?.requestedOrientation ?: -1
         activity?.requestedOrientation = ActivityInfo.SCREEN_ORIENTATION_NOSENSOR
+        if (savedInstanceState == null) {
             viewModel.startFlashing()
         }
+    }
 
     @SuppressLint("WrongConstant")
     override fun onDestroyView() {