Fix UI crash when user navigates away before the download dialog appears

Author: letenger

app/src/main/java/org/schabi/newpipe/info_list/dialog/StreamDialogDefaultEntry.java

@@ -113,7 +113,7 @@ public enum StreamDialogDefaultEntry {
     DOWNLOAD(R.string.download, (fragment, item) ->
             fetchStreamInfoAndSaveToDatabase(fragment.requireContext(), item.getServiceId(),
                     item.getUrl(), info -> {
-                        if (fragment.getContext() != null) {
+                        if (fragment.isAdded() && !fragment.isStateSaved()) {
                             final DownloadDialog downloadDialog =
                                     new DownloadDialog(fragment.requireContext(), info);
                             downloadDialog.show(fragment.getChildFragmentManager(),