Catch if module file is not set

When loading .net assemblies after import clr, the file attribute is present but not set, causing the autoreload module to not work appropriately.

IPython/extensions/autoreload.py

@@ -183,7 +183,7 b' class ModuleReloader(object):'
         return top_module, top_name
 
     def filename_and_mtime(self, module):
-        if not hasattr(module, '__file__'):
+        if not hasattr(module, '__file__') or module.__file__ is None:
             return None, None
 
         if module.__name__ == '__main__':