adding rayan prompt

app.py

@@ -500,7 +500,7 @@ if st.session_state.get('button') == True:
                     chars_out = dict(zip(chars, sel_var_values))
                     sorted_chars_out = sorted(chars_out.items(), key=lambda x: x[1], reverse=True)
             prefrence_variables=["charcter counts: "+str(x)+", Target Rate: "+str(y) for x,y in zip(chars,sel_var_values)]
-            prefrence_variables=['']+prefrence_variables
+            prefrence_variables=[None]+prefrence_variables
             preference = st.selectbox(
                         'Please select your preferences for target metric',
                         prefrence_variables,