Don't treat a 404 as a fatal error

src/api/fanart_api.js

@@ -19,18 +19,26 @@ class FanartApi {
                 timeout: 2000,
             },
         }).then((response) => {
+            if (response.status === 404) {
+                return null;
+            } else {
                 return response.text().then(text => {
                     return {
                         ok: response.ok,
                         body: text,
                     }
                 });
+            }
         }).then((data) => {
+            if (data === null) {
+                return null;
+            } else {
                 const {ok, body} = data;
                 if (!ok) {
                     throw new Error(`${url}: ${body}`);
                 }
                 return JSON.parse(body);
+            }
         }).catch(err => {
             console.error(err);
             return null;