FrameIO: Sync FrameIO Directory failed when some Assets are Queued status in FrameIO folder

When user upload Assets in FrameIO, sometimes it's queued status, at this time, if user on nuxeo side want to sync up Frameio directory, the action will be failed, the reason is in FrameioServiceImpl.createAssetDocument: https://github.com/nuxeo/nuxeo-frameio/blob/3c6f0de50ce338a569af49efa2179207c1ec4d8f/nuxeo-frameio/src/main/java/org/nuxeo/ecm/frameio/service/FrameioServiceImpl.java#L303 - see the attached file Assets-526.zip

FrameioService will get Asset's metadata when syncing, but the Asset's metadada doesn't exist, so FrameioService will get null, throw exception and terminate the syncing flow.

AC:

Skip the failed Asset, continue to sync up left Assets or give user a configurable settings, such as 'continueOnFailure=true/false'