Change in file path for downloaded files crashes app

I have tried thrice to change the file path for downloaded files. App has crashed every time.

### Cause of error
```java
Exception in thread "AsyncTask #1" java.lang.RuntimeException: An error occurred while executing doInBackground()
at android.os.AsyncTask$4.done(AsyncTask.java:415)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
at java.util.concurrent.FutureTask.run(FutureTask.java:271)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:923)
Caused by: Exception in thread "AsyncTask #1" java.lang.RuntimeException: com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask$MigrationException
at com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask.checkDestinationAvailability(StorageMigration.java:432)
at com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask.doInBackground(StorageMigration.java:379)
at com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask.doInBackground(StorageMigration.java:335)
at android.os.AsyncTask$3.call(AsyncTask.java:394)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:923)
Caused by: Exception in thread "AsyncTask #1" com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask$MigrationException
at com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask.checkDestinationAvailability(StorageMigration.java:429)
at com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask.doInBackground(StorageMigration.java:379)
at com.owncloud.android.ui.activity.StorageMigration$FileMigrationTask.doInBackground(StorageMigration.java:335)
at android.os.AsyncTask$3.call(AsyncTask.java:394)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:923)

```

### App information
* ID: `com.nextcloud.client`
* Version: `30300590`
* Build flavor: `generic`

### Device information
* Brand: `Fairphone`
* Device: `FP3`
* Model: `FP3`
* Id: `8901.4.A.0023.0`
* Product: `FP3`

### Firmware
* SDK: `30`
* Release: `11`
* Incremental: `gms-e1827e20`