Export to Json not handling nulls correctly.

[gustavofarias]

When I use Json metadata on my report and export to json, when a text field evaluates to a null value, instead of printing this: {... "field"=null ...} it's being printed this: {... "field"="null" ...}.

Jasperreports is handling null as the String "null". If I set the field to "blank when null" this is printed: {... "field"="" ...}