Guard against self.state is None

IPython/sphinxext/ipython_directive.py

@@ -429,6 +429,9 b' class EmbeddedSphinxShell(object):'
             ret.append('')
 
         # context information
+        filename = "Unknown"
+        lineno = 0
+        if self.state:
         filename = self.state.document.current_source
         lineno = self.state.document.current_line