Treat empty string value in numeric field as a nan
Treat empty string value in numeric field as a nan

Otherwise, empty string values, such as those read from empty cells in a spreadsheet, have to be converted manually ahead of time to None or np.nan, which is a real pain.
dimitri-yatsenko/datajoint-python,fabiansinz/datajoint-python,eywalker/datajoint-python,datajoint/datajoint-python