fix: Add null checks for districtFetch results Refs: PALVELUKARTTA-UI-A0

[sentry]

This PR addresses the TypeError: Cannot read properties of undefined (reading 'results') that occurred when districtFetch resolved with undefined.

The root cause was identified as the handleFetch utility (used by districtFetch) silently resolving with undefined on network errors, combined with calling components not defensively checking the resolved data before accessing properties like .results.

To fix this, null/undefined checks have been added at the call sites of districtFetch:

• In src/views/AreaView/AreaView.js, a data?.results guard was added before dispatching setDistrictAddressData, and a .catch(() => {}) was added to the promise chain to prevent unhandled rejections.
• In src/views/AddressView/utils/fetchAdministrativeDistricts.js, an early return if (!districtData?.results) return []; was added.
• In src/views/DivisionView/fetchDivisionDistrict.js, a similar early return if (!districtData?.results) return []; was added.

These changes ensure that the application gracefully handles cases where districtFetch does not return valid data, preventing crashes.

Fixes PALVELUKARTTA-UI-A0

Refs: PL-280

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[azure-pipelines]

PALVELUKARTTA-UI branch is deployed to platta: https://palvelukartta-ui-pr1363.dev.hel.ninja 🚀🚀🚀