Fix FileDetailFragmentStaticServerIT failing

Signed-off-by: ZetaTom <70907959+ZetaTom@users.noreply.github.com>

app/src/main/java/com/owncloud/android/ui/fragment/FileDetailSharingFragment.java

@@ -452,7 +452,11 @@ public class FileDetailSharingFragment extends Fragment implements ShareeListAda
      * before reading database.
      */
     public void refreshSharesFromDB() {
-        file = fileDataStorageManager.getFileById(file.getFileId());
+        OCFile newFile = fileDataStorageManager.getFileById(file.getFileId());
+        if (newFile != null) {
+            file = newFile;
+        }
+
         ShareeListAdapter adapter = (ShareeListAdapter) binding.sharesList.getAdapter();
 
         if (adapter == null) {