validate max_words_per_line input type and provide default

src/transcriber.py

@@ -109,6 +109,8 @@ def transcriber(file_input:gr.File,
                 task:str,
                 model_version:str,
                 device_type: str):
+    if not isinstance(max_words_per_line, int):
+        max_words_per_line = 6
     srt_filepath = os.path.normpath(f"{file_input.split('.')[0]}.srt")
     if file_type == "video" :
         audio_input = convert_video_to_audio(file_input)