TypeError: propValue is not iterable

[diox]

A variation of #4645 which we've seen in 2023.01.12 tag:
https://sentry.io/organizations/mozilla/issues/3364574696/events/30d0e66e32fe4ba1a428ff9d60ff07c2/?project=6310819

propValue is not iterable

/data/olympia/node_modules/addons-linter/dist/webpack:/addons-linter/src/schema/validator.js:617
      for (const permission of propValue) {
                               ^
TypeError: propValue is not iterable
    at Ajv.validateAddon (/data/olympia/node_modules/addons-linter/dist/webpack:/addons-linter/src/schema/validator.js:617:32)
    at validate15 (eval at compileSchema (/data/olympia/node_modules/ajv/lib/compile/index.ts:171:26), <anonymous>:3:44801)
    at SchemaValidator.validate14 [as _addonValidator] (eval at compileSchema (/data/olympia/node_modules/ajv/lib/compile/index.ts:171:26), <anonymous>:3:213)
    at validate (/data/olympia/node_modules/addons-linter/dist/webpack:/addons-linter/src/schema/validator.js:773:27)
    at ManifestJSONParser._validate (/data/olympia/node_modules/addons-linter/dist/webpack:/addons-linter/src/parsers/manifestjson.js:440:20)
    at new ManifestJSONParser (/data/olympia/node_modules/addons-linter/dist/webpack:/addons-linter/...

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