fix for missing cell_number in iframe renderer

Author: nicolaskruchten

Diff for: packages/python/plotly/plotly/io/_base_renderers.py

@@ -609,11 +609,13 @@ def to_mimebundle(self, fig_dict):
 
     def build_filename(self):
         ip = IPython.get_ipython() if IPython else None
-        cell_number = list(ip.history_manager.get_tail(1))[0][1] + 1 if ip else 0
-        filename = "{dirname}/figure_{cell_number}.html".format(
+        try:
+            cell_number = list(ip.history_manager.get_tail(1))[0][1] + 1 if ip else 0
+        except Exception:
+            cell_number = 0
+        return "{dirname}/figure_{cell_number}.html".format(
             dirname=self.html_directory, cell_number=cell_number
         )
-        return filename
 
     def build_url(self, filename):
         return filename