Fix broken initial page load by excluding our own JavaScript. Also return 404 on error.

src/fetcher.js

@@ -77,7 +77,9 @@ self.addEventListener('fetch', (event) => {
     // If this isn't an IPFS URL, bail.
     if (!multihash.startsWith('/ipfs/')) {
         console.log('not a valid IPFS hash:', multihash)
-        event.respondWith(not_found_response())
+        if (multihash != '/bundle.js' && multihash != '/fetcher.js') {
+            event.respondWith(not_found_response())
+        }
         return
     }
 
@@ -115,6 +117,7 @@ self.addEventListener('fetch', (event) => {
             return not_found_response()
         }).catch((error) => {
             console.log(error)
+            return not_found_response()
         })
     )
 })