Always show a button to launch gradation, even in case of error

ui/src/routes/works/[wid]/rendus/+page.svelte

@@ -162,6 +162,15 @@
                                                     >
                                                         <i class="bi bi-play"></i>
                                                     </button>
+                                                {:catch err}
+                                                    <button
+                                                        class="btn btn-sm mr-1 btn-outline-dark"
+                                                        class:disabled={!show_dl_btn[user.id]}
+                                                        title={JSON.stringify(err)}
+                                                        on:click={() => { repo.runGradation(); }}
+                                                    >
+                                                        <i class="bi bi-play"></i>
+                                                    </button>
                                                 {/await}
                                                 <a
                                                     href="/api/users/{user.id}/works/{w.id}/repositories/{repo.id}/traces"