Add null guard before spreading error.response.data.detail in uploadLog

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/stores/files.ts

@@ -217,7 +217,8 @@ export const useFilesStore = defineStore("filesStore", {
         this.$router.push({ name: "Files" });
       } catch (error) {
         if (error.response?.status === 422) {
-          const detail = [...error.response.data.detail];
+          const raw = error.response.data?.detail;
+          const detail = Array.isArray(raw) ? [...raw] : [];
 
           uploadFailedSecond(detail);
         } else {