Improve messages when inputs are missing

app.py

@@ -123,10 +123,6 @@ def _parse_metrics(metrics):
 
 
 def _create_model_card():
-    if model is None or data is None:
-        st.text("*some data is missing to render the model card*")
-        return
-
     init_repo()
     metadata = card.metadata_from_config(hf_repo)
     model_card = card.Card(model=model, metadata=metadata)
@@ -217,8 +213,7 @@ def _process_card_for_rendering(rendered: str) -> tuple[str, str]:
     return metadata, rendered_with_img
 
 
-def display_model_card():
-    model_card = _create_model_card()
+def display_model_card(model_card):
     if not model_card:
         return
 
@@ -235,8 +230,7 @@ def display_model_card():
         st.markdown(rendered, unsafe_allow_html=True)
 
 
-def download_model_card():
-    model_card = _create_model_card()
+def download_model_card(model_card):
     if model_card is not None:
         return model_card.render()
     return ""
@@ -380,9 +374,17 @@ with left_col:
 
 
 with right_col:
+    model_card = None
+    if model is None:
+        st.text("*add a model to render the model card*")
+    if data is None:
+        st.text("*add data to render the model card")
+    if (model is not None) and (data is not None):
+        model_card = _create_model_card()
+
     # this contains the rendered model card
-    rendered = download_model_card()
+    rendered = download_model_card(model_card)
     if rendered:
         st.download_button(label="Download model card (markdown format)", data=rendered)
 
-    display_model_card()
+    display_model_card(model_card)