add safeguard for looking up empty string

app.py

@@ -76,6 +76,9 @@ Returns:
     - contextualization_weights: gr.State variable, stores the contextualization weights for the input sentence
 """
 def predict_next_word (sentence, top_k = 5, contextualization_weights = None):  
+    
+    if sentence == "":
+        return None, None, None, None
 
     # For better tokenization, by default, adds a space at the beginning of the sentence if it doesn't already have one
     # and remove trailing space
@@ -282,10 +285,9 @@ with gr.Blocks( theme = gr.themes.Base(),
                 selected_token = gr.Textbox(label="Current Selected Token", interactive=False)
             with gr.Column(scale=8):
                 gr.Markdown("""####
-                Once a token is chosen, you can **use the sliders below to change the weights of any senses** for that token, \
+                Once a token is chosen, you can **use the sliders below to change the weight of any sense** for that token, \
                     and then click "Predict next word" to see updated next-word predictions. \
-                    You can change the weights of *multiple senses of multiple tokens;* \
-                    changes will be preserved until you click "Reset weights".
+                    You can change the weights of *multiple senses of multiple tokens*. Erase all changes with "Reset weights".
                 """)
         # sense sliders and top sense words dataframes
         with gr.Row():