Update app.py

app.py

@@ -33,13 +33,14 @@ else:
     
 paper = get_paper(pname)
 
-name = paper.title+'.pdf'
-name = name.replace('?', '')
-name = "downloads/" + name
-
-tpages = len(list(extract_pages(name)))
-print("total pages=", tpages)
-pgs = [i+1 for i in range(tpages)]
+if paper:
+  name = paper.title+'.pdf'
+  name = name.replace('?', '')
+  name = "downloads/" + name
+  
+  tpages = len(list(extract_pages(name)))
+  print("total pages=", tpages)
+  pgs = [i+1 for i in range(tpages)]
 
 with st.form(key = "paper_form"):
   col1, col2 = st.columns(3)