Add test_no_results_with_connection_as_dict
pymssql.pyx: Check self.description not

before looking at column names

Prevents errors or crashes when as_dict=True and executing queries with
no results like CREATE TABLE, INSERT, etc.
Merge pull request #168 from pymssql/as_dict_No_column_name_raise_exception2

pymssql.pyx: Check self.description not None before looking at column names