fix: Skip empty files in metadata providers

[juliushaertl]

Avoid errors in the log when being called with an empty file:

{
  "reqId": "vjssIBquwyINBtapTLW9",
  "level": 3,
  "time": "2023-12-04T07:45:18+00:00",
  "remoteAddr": "",
  "user": "admin",
  "app": "PHP",
  "method": "",
  "url": "--",
  "message": "exif_read_data(): File too small (0) at /var/www/html/apps-extra/photos/lib/Listener/ExifMetadataProvider.php#75",
  "userAgent": "--",
  "version": "29.0.0.2",
  "data": {
    "app": "PHP"
  }
}
{
  "reqId": "vjssIBquwyINBtapTLW9",
  "level": 3,
  "time": "2023-12-04T07:45:18+00:00",
  "remoteAddr": "",
  "user": "admin",
  "app": "PHP",
  "method": "",
  "url": "--",
  "message": "getimagesizefromstring(): Error reading from ! at /var/www/html/apps-extra/photos/lib/Listener/SizeMetadataProvider.php#56",
  "userAgent": "--",
  "version": "29.0.0.2",
  "data": {
    "app": "PHP"
  }
}

[juliushaertl]

These cypress tests also fails on other PRs

[juliushaertl]

/backport to stable28