Fix magn 3738 BuiltinFunction Transpose({{}}) returns {{null}}

This pull request fixes defect [MAGN 3738 BuiltinFunction Transpose({{}}) returns {{null}}](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-3738).

2D empty array ``{{}}`` should return empty array ``{}`` instead of ``{{null}}``, as the number of column is 0. 

Regression test case added.

@junmendoza  please review the change.