fix: edge case (empty string in csv-rows-to-columns)

src/pages/tools/csv/csv-rows-to-columns/service.ts

@@ -17,12 +17,18 @@ export function csvRowsToColumns(
   customFiller: string,
   commentCharacter: string
 ): string {
+  if (!input) {
+    return '';
+  }
+
   const rows = input
+    ? input
         .split('\n')
         .map((row) => row.split(','))
         .filter(
           (row) => row.length > 0 && !row[0].trim().startsWith(commentCharacter)
-    );
+        )
+    : [];
   const columnCount = Math.max(...rows.map((row) => row.length));
   for (let i = 0; i < rows.length; i++) {
     for (let j = 0; j < columnCount; j++) {