Add null guards for getElementById and uploadDetail in UploadPage

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

src/views/Upload/UploadPage.vue

@@ -452,6 +452,7 @@ onMounted(async () => {
     (newValue) => {
       if (newValue) {
         const inputElement = document.getElementById("fileNameInput");
+        if (!inputElement) return;
         const baseWidth = 20;
         const textWidth = getTextWidth(fileName.value, inputElement);
         inputElement.style.width = baseWidth + textWidth + "px";
@@ -461,10 +462,12 @@ onMounted(async () => {
   );
   showEdit.value = true;
   if (uploadId.value) await filesStore.getUploadDetail();
+  if (uploadDetail.value?.columns) {
     selectedColumns.value = Array.from(
       { length: uploadDetail.value.columns.length },
       () => columnType[columnType.length - 1],
     ); // Default to "Not Assigned"
+  }
   unwatch();
   isLoading.value = false;
 });