VODBAlias function returns NULL instead NULL_STRING

[leon-ts]

The VODBAlias function in VO returns NULL_STRING if the workarea number passed is invalid (does not exist). This behavior is documented, including X#. But actually X# returns NULL in this situation. As a result, in already existing programs, where the result of the VODBAlias function is checked against NULL_STRING, the check fails.

P.S. NULL_STRING = empty string "" (/vo2)

[RobertvanderHulst]

The function (Actually the Workareas.GetAlias() method) now returns String.Empty in these cases.

[cpyrgas]

Confirmed fixed.