TAJO-1099: LogicalPlanner::convertDataType causes NPE in some cases.

So far, ExprTestBase has not passed through TypeDeterminant in LogicalPlanPreprocessor. So, unit tests haven't caused this problems. 

I fixed the bug and modified LogicalPlanPreprocessor to pass TypeDeterminant in LogicalPlanPreprocessor. As a result, even though this patch does not include any unit tests, it is same as all ExprTestBase tests verify this problem.