library_idbfs.js: Handle transaction.onabort in reconcile()

If the transaction aborts (which can happen due to, for example, a QuotaExceededError), `onabort` must be handled to ensure that the `callback` actually gets called.

src/library_idbfs.js

@@ -280,6 +280,12 @@ addToLibrary({
         }
       };
 
+      // transaction may abort if (for example) there is a QuotaExceededError
+      transaction.onabort = (e) => {
+        done(event.target.error); // DOMException
+        e.preventDefault();
+      };
+
       // sort paths in ascending order so directory entries are created
       // before the files inside them
       create.sort().forEach((path) => {