overwriting json files in drive breaks kernels

[DerThorsten]

overwriting json stored in the lite drive will break the kernel. In xeus-python one can reproduce this via: (this also fails for other kernels (xeus-r for instance))

s = R"""
{
  "args": {}
}
"""
import json
data = json.loads(s)
with open('data.json', 'w') as f:
    json.dump(data, f)
with open('data.json', 'w') as f:
    json.dump(data, f)

the kernel will be in a busy state forever and we see this error in the dev-console

VM2772:1 Uncaught (in promise) SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at R.put (drivecontents.js:118:24)
    at R.processDriveRequest (drivecontents.js:30:29)
    at h._onDriveMessage (service-worker-manager.js:49:65)
    at BroadcastChannel._onBroadcastMessage (service-worker-manager.js:45:22)

I observed the following: in drivecontent.js when trying to save / overwrite a json which already in the drive, we see request.data.data = "" ie its only an empty string.