Error log info

[Greg Buchanan]

i am trying to diagnose some odd behavior of jetspeed-1 and found this
in the velocity log:
 
2004-06-22 17:17:58,621 - RHS of #set statement is null. Context will
not be modified. /controls/html/jetspeed-tab.vm [line 36, column 1]
 
Can anyone explain this to me or point me to documentation which
describes this error. I looked in the file and it is references colors,
skins, etc. Not sure if it's an error or not. 
 
Thanks.