Column view odd behaviour on emptying field

Column view odd behaviour on emptying field

[Johnny]

I am trying to learn the org-taskjuggler mode and following the tutorial
on http://orgmode.org/worg/org-tutorials/org-taskjuggler.html. Another
great feature of org-mode! 

Anyhow, this uses Column View extensive, and I noticed a strange
behaviour if setting a column field and subsequently emptying it. It
seems the property remains, but is blanked and thus disabled, and when
setting the property again to an allowed value, a new property field is
created. The propery is not displayed in column view, presumably because
of the remaining broken (empty) property from the previous erase.

1) Property set
*** Database coupling
    :PROPERTIES:
    :Effort:   20.0
    :allocate: doc
    :END:

2) Property cleared 
*** Database coupling
    :PROPERTIES:
    :Effort:   20.0
    :allocate: 
    :END:

3) Property set again
*** Database coupling
    :PROPERTIES:
    :Effort:   20.0
    :allocate: 
    :allocate: test
    :END:

Regards,
-- 
Johnny