fix bug of rewrite

gradio_app.py

@@ -235,15 +235,14 @@ def generate_motion_func(
 ) -> Tuple[str, List[str]]:
     use_prompt_engineering = USE_PROMPT_ENGINEERING
     output_dir = "output/gradio"
-    # When rewrite is not available, use original_text directly
-    if use_prompt_engineering:
+    # Determine which text to use: prefer rewritten_text, fallback to original_text
+    if use_prompt_engineering and rewritten_text.strip():
         text_to_use = rewritten_text.strip()
-        if not text_to_use:
-            return "Error: Rewritten text is empty, please rewrite the text first", []
-    else:
+    elif original_text.strip():
         text_to_use = original_text.strip()
-        if not text_to_use:
-            return "Error: Input text is empty, please enter text first", []
+    else:
+        # Both are empty
+        return "Error: Input text is empty, please enter text first", []
 
     try:
         # Use runtime from global if available (for Zero GPU), otherwise use self.runtime