Omit missing years from upload destination paths

packages/i18n/locales/en/errors.json

@@ -104,6 +104,7 @@
     "no_target": "No storage accepts uploads (or several do and none is the default)",
     "no_template": "The storage has no path template",
     "missing_field": "Not enough metadata to build the storage path",
+    "missing_year": "Year is missing — check the metadata. The year is omitted from the path",
     "offset_mismatch": "The upload got out of sync; try again",
     "size_mismatch": "The file size does not match the declared one",
     "hash_mismatch": "The file was corrupted in transit (SHA-256 mismatch)",