Downgrade gracefully if window.caches is not available.

This should not happen in production, as the Cache API is
widely implemented as of the date of this commit, but it
will not be available if the user is not in a secure
context. That should only happen during testing.

lib/www/client/source/src/lib/deck.gl/DougalBinaryLoader.js

@@ -19,7 +19,7 @@ async function cachedFetch(url, init, opts = {}) {
       }
     }
 
-    if (opts?.cache) {
+    if (opts?.cache && window.cache) {
       cache = await caches.open(opts.cache.name);
       res = await cache.match(url);
       isCached = !!res;

lib/www/client/source/src/store/modules/api/actions.js

@@ -61,7 +61,7 @@ async function api ({state, getters, commit, dispatch}, [resource, init = {}, cb
       }
     }
 
-    if (opts?.cache) {
+    if (opts?.cache && window.caches) {
       cache = await caches.open(opts.cache.name);
       res = await cache.match(url);
       isCached = !!res;

lib/www/client/source/src/views/Map.vue

@@ -879,6 +879,7 @@ export default {
     },
 
     async refresh () {
+      if (window.caches) {
         const cache = await caches.open("dougal");
         for (const key of await cache.keys()) {
           // Match only resolved requests
@@ -889,6 +890,7 @@ export default {
             }
           }
         }
+      }
       await this.$root.sleep(300);
       this.getSequenceData();
     },