Fix transparency on RGBA images

app.py

@@ -125,7 +125,7 @@ def process_question(question, document, model=list(CHECKPOINTS.keys())[0]):
         return None, None
 
     predictions = run_pipeline(model, question, document, 3)
-    pages = [x.copy() for x in document.preview]
+    pages = [x.copy().convert("RGB") for x in document.preview]
     for i, p in enumerate(ensure_list(predictions)):
         if i > 0:
             # Keep the code around to produce multiple boxes, but only show the top