Fixed: Application crashes at first launch.

Author: MohitMaliDeveloper

app/src/main/java/org/kiwix/kiwixmobile/nav/destination/reader/KiwixReaderFragment.kt

@@ -257,9 +257,10 @@ class KiwixReaderFragment : CoreReaderFragment() {
     when (restoreOrigin) {
       FromExternalLaunch -> {
         coreReaderLifeCycleScope?.launch {
+          if (!isAdded) return@launch
           val settings =
-            requireActivity().getSharedPreferences(SharedPreferenceUtil.PREF_KIWIX_MOBILE, 0)
-          val zimReaderSource = fromDatabaseValue(settings.getString(TAG_CURRENT_FILE, null))
+            activity?.getSharedPreferences(SharedPreferenceUtil.PREF_KIWIX_MOBILE, 0)
+          val zimReaderSource = fromDatabaseValue(settings?.getString(TAG_CURRENT_FILE, null))
           if (zimReaderSource?.canOpenInLibkiwix() == true) {
             if (zimReaderContainer?.zimReaderSource == null) {
               openZimFile(zimReaderSource, isFromManageExternalLaunch = true)

core/src/main/java/org/kiwix/kiwixmobile/core/main/CoreReaderFragment.kt

@@ -1220,6 +1220,7 @@ abstract class CoreReaderFragment :
   override fun onDestroyView() {
     super.onDestroyView()
     try {
+      coreReaderLifeCycleScope?.cancel()
       readerLifeCycleScope?.cancel()
       readerLifeCycleScope = null
     } catch (ignore: Exception) {