Update app.py (#2)

- Update app.py (ddf0b1940b46bebe4f9bbf9c1e00156074cc96fa)

app.py

@@ -4,7 +4,7 @@ import io
 
 def create_file(text):
     cal_text = backend.generate_text(text)
-    if cal_text is "":
+    if cal_text == "":
         raise gr.Error("No calendar data could be generated from the input.")
     else:
         file_obj = io.BytesIO(cal_text.encode("utf-8"))