Do cheaper check for column having a type.

        # Special-case implicit M2M tables

        if isinstance(field, ManyToManyField) and field.rel.through._meta.auto_created:

            return self.delete_model(field.rel.through)

        # Get the column's definition

        definition, params = self.column_sql(model, field)

        # It might not actually have a column behind it

        if definition is None:

        if field.db_parameters(connection=self.connection)['type'] is None:

            return

        # Get the column's definition

        definition, params = self.column_sql(model, field)

        # Delete the column

        sql = self.sql_delete_column % {

            "table": self.quote_name(model._meta.db_table),