created an attachment (id=160600)
screenshot

description:
"preview with format" is blank when select custom for "format datetime".

build number:
2.6.0.v20100302-0630

steps to reproduce:
1. new a data.
2. go to property editor->format datetime.
3. select "custom" for "format as".
4. check "preview with format".

expected result:
the value is shown for format number and "format string" but not for "format datetime".

actual result:
see the screenshot.

error log:
n/a
if no the format code,show the string in the 'preview with format' label.
fixed it.
verified in build (2.6.0.v20100428-0630), closed.