Queue attempts to get file contents for deleted or non-existent files

[dangur]

When running the foia_submissions queue, files that are not present generate a warning when the file_get_contents function is unable to accept the lack of an argument.

Acceptance criteria

• Running the queue with a deleted or otherwise non-present file should not generate a warning.

Expected Behavior

Running the queue does not attempt to process files which have been deleted from the filesystem.

Actual Behavior

Running the queue results in a warning:

file_get_contents(test.txt):  [warning]
failed to open stream: No such file or directory EmailWebformHandler.php:812
Processed 1 items from the foia_submissions queue

Steps to reproduce the behavior

1. Upload a test virus file to a foia request form
2. Wait for the files and request entity to update on cron tasks that call drush feu, drush qcr, and drush queue-run or run manually
3. See the notice above returned when drush queue-run is run