fail when transcriptions contain a newline

kaldi_data_generator/main.py

@@ -312,6 +312,10 @@ class HTRDataGenerator:
                 if not text or not text.strip():
                     continue
 
+                if "\n" in text.strip():
+                    elem_id = res["element"]["id"]
+                    raise ValueError(f"Newlines are not allowed in line transcriptions - {page_id} - {elem_id} - {text}")
+
                 if "zone" in res:
                     polygon = res["zone"]["polygon"]
                 elif "element" in res: