Handle invalid/empty start_page_num inputs in jump_to_page function safely

app.py

@@ -571,7 +571,11 @@ with gr.Blocks(title="Maya: Immersive Manga AI", css=CUSTOM_CSS) as demo:
     def jump_to_page(pdf, page_num_val):
         if not pdf:
             return gr.update(), "Upload a PDF first", 0
-        page_idx = max(0, int(page_num_val) - 1)
+        try:
+            val = int(page_num_val)
+            page_idx = max(0, val - 1)
+        except (ValueError, TypeError):
+            page_idx = 0
         return load_comic_page(pdf, page_idx)
 
     start_page_num.submit(