Fix handling of acoustid network errors
Fix stash-pop generated error

I tested this before a stash but failed to retest it after a stash pop.
Sigh.
Address minor zas comment
Address zas, freso comments
Address zas comment
Address final zas comment
Merge pull request #241 from Sophist-UK/sophist_fix_acoustid_webservice_errors

Fix handling of acoustid network errors