Fix network error

Some users experience network errors with at least one reason being:

wuhan-coronavirus-api.laeyoung.endpoint.ainize.ai/jhu-edu/timeseries?iso2=DE&onlyCountries=true:1 Failed to load resource: net::ERR_NAME_NOT_RESOLVED
The FetchEvent for "https://cv19.gitlab.io/" resulted in a network error response: the promise was rejected.
workbox-strategies.prod.js:1 Uncaught (in promise) no-response: no-response :: [{"url":"https://cv19.gitlab.io/"}]
    at a.makeRequest (https://cdn.jsdelivr.net/npm/workbox-cdn@4.3.1/workbox/workbox-strategies.prod.js:1:2145)