Handle invalid data returned by the server when uploading a chunk

JSONDecodeError: Expecting value: line 1 column 1 (char 0)
  File "nxdrive/engine/processor.py", line 344, in _execute
  File "nxdrive/engine/processor.py", line 242, in _handle_doc_pair_sync
  File "nxdrive/engine/processor.py", line 992, in _synchronize_locally_created
  File "nxdrive/client/remote_client.py", line 634, in stream_file
  File "nxdrive/client/remote_client.py", line 493, in upload
  File "nxdrive/client/uploader/sync.py", line 31, in upload
  File "nxdrive/client/uploader/__init__.py", line 212, in upload_impl
  File "nxdrive/client/uploader/__init__.py", line 297, in upload_chunks
  File "nuxeo/handlers/default.py", line 225, in iter_upload
  File "nuxeo/uploads.py", line 177, in send_data
  File "nuxeo/endpoint.py", line 127, in post
  File "requests/models.py", line 900, in json
  File "__init__.py", line 346, in loads
  File "json/decoder.py", line 337, in decode
  File "json/decoder.py", line 355, in raw_decode