Update app.py

app.py

@@ -190,6 +190,8 @@ def greet(operation,filer):
         if item.endswith(".sav") and int(item.split("=")[0]) > maxnum:
             maxnum = int(item.split("=")[0])
             modelname = item
+    if maxnum == 0:
+        return None,"No model found, please use retrain operation to build one"
     #modelname = "VotingClassifier=0.95756598831352.sav"
     loaded_model = pickle.load(open(modelname, 'rb'))
     droppers = 0