Update app.py

app.py

@@ -90,10 +90,12 @@ def main():
   text_list = []
   causal_sents = []
   uploaded_file = PdfReader('sample_anno.pdf')
-  try:
+  #try:
+  if uploaded_file is not None:
     uploaded_file = st.sidebar.file_uploader("Choose a file", type = "pdf")
     #st.stop()
-  except:
+  else:
+  #except:
     #if uploaded_file 
     st.write("Upload a pdf file...")
     st.stop()