Update app.py

app.py

@@ -451,7 +451,7 @@ def vocab_level_inter(text):
         continue
     lvl = int(get_level(i))/4
     interp.append((i, lvl))
-    if int(level) < 0:
+    if int(lvl) < 0:
         continue
     sum+= lvl
     total += 1