Update app.py

app.py

@@ -7,8 +7,11 @@ def main():
     st.title('EN sentence mask filling')
     st.markdown('Mask a word with [MASK]. For example, **I [MASK] dog for a walk**')
     masked = st.text_input('Masked sentence','Please insert a sentence')
- 
-    output = unmasker(masked)
+    
+    if '[MASK]' is in masked.split(' '):
+        output = unmasker(masked)
+    else:
+        print('Sentence is not masked!!!')
   
 if __name__ == "__main__":
     main()