trying none as an input

app.py

@@ -42,13 +42,10 @@ sub = st.sidebar.selectbox(
 )
 
 st.sidebar.title("Write a Custom Prompt")
-cap_prompt = st.text_input(
+cap_prompt = st.sidebar.text_input(
     "Leave this blank for an unbiased caption", 
-    value="This is a photo of"
+    value=None
 )
-st.write("=====================")
-st.write(cap_prompt)
-st.write("=====================")
 
 if st.sidebar.button("Random Sample Image"):
     random_image = get_rand_img(sample_images)