fix- json syntax exceptions

[alperozturk96]

Issue

When nothing changes, API processes empty Reader then it is causing JsonSyntaxException.

SSO PR: nextcloud/Android-SingleSignOn#910

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1 path $
See https://github.com/google/gson/blob/main/Troubleshooting.md#unexpected-json-structure
	at com.google.gson.Gson.fromJson(Gson.java:1381)
	at com.google.gson.Gson.fromJson(Gson.java:1259)
	at com.google.gson.Gson.fromJson(Gson.java:1227)
	at com.nextcloud.android.sso.api.NextcloudAPI.convertStreamToTargetEntity(NextcloudAPI.java:136)
	at com.nextcloud.android.sso.api.NextcloudAPI.lambda$performRequestObservableV2$0(NextcloudAPI.java:98)
	at com.nextcloud.android.sso.api.NextcloudAPI.$r8$lambda$af7W9mq2B0ZrhVJwZd-ibFp8T3Y(Unknown Source:0)
	at com.nextcloud.android.sso.api.NextcloudAPI$$ExternalSyntheticLambda2.subscribe(D8$$SyntheticClass:0)
	at io.reactivex.internal.operators.observable.ObservableFromPublisher.subscribeActual(ObservableFromPublisher.java:31)
	at io.reactivex.Observable.subscribe(Observable.java:12284)
	at io.reactivex.internal.operators.observable.ObservableSingleMaybe.subscribeActual(ObservableSingleMaybe.java:31)
	at io.reactivex.Maybe.subscribe(Maybe.java:4290)
	at io.reactivex.Maybe.blockingGet(Maybe.java:2320)
	at io.reactivex.Observable.blockingSingle(Observable.java:5381)
	at it.niedermann.owncloud.notes.persistence.NotesServerSyncTask.pullRemoteChanges(NotesServerSyncTask.java:229)
	at it.niedermann.owncloud.notes.persistence.NotesServerSyncTask.run(NotesServerSyncTask.java:101)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:520)
	at java.util.concurrent.FutureTask.run(FutureTask.java:317)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1154)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:652)
	at java.lang.Thread.run(Thread.java:1563)
Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1 path $
See https://github.com/google/gson/blob/main/Troubleshooting.md#unexpected-json-structure
	at com.google.gson.stream.JsonReader.unexpectedTokenError(JsonReader.java:1831)
	at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:470)
	at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:82)
	at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:64)
	at com.google.gson.Gson.fromJson(Gson.java:1358)
	... 19 more

Changes

Ignores empty response

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/2883.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.

[alperozturk96]

/backport to stable-4.5

[alperozturk96]

Android Files application is responsible for handling 304 response, thus this PR is not valid anymore.

Note

Sometimes the loading indicator in the Notes app gets stuck due to the current behavior of InputStreamBinder in the Files application and how it is handled in the SSO library. This needs to be addressed in a separate PR