Add a retry button.

frontend/src/components/uploading_side_bar.tsx

@@ -91,6 +91,13 @@ function TaskTile({task}: {task: UploadingTask}) {
     <progress className="progress progress-primary my-2" value={100 * progress} max={100} />
     {error && <p className={"text-error p-1"}>{error}</p>}
     <div className={"my-2 flex flex-row-reverse"}>
+      {
+        error && <button className={"btn h-7 mr-1"} onClick={() => {
+          task.start();
+        }}>
+          Retry
+        </button>
+      }
       <button className={"btn btn-error h-7"} onClick={() => {
         const dialog = document.getElementById(`cancel_task_${task.id}`) as HTMLDialogElement;
         dialog.showModal();

frontend/src/network/uploading.ts

@@ -124,6 +124,7 @@ export class UploadingTask extends Listenable {
   }
 
   async start() {
+    this.errorMessage = null;
     this.status = UploadingStatus.UPLOADING;
     this.notifyListeners();
     await Promise.all([