test build:2.6.0.v20100329-0630

steps to reproduce:
1. insert an image, select file from resource folder, set type as javascript
2. edit the image, change nothing but click right side button to change javascript syntax to constant

expected result:ok button in image build is enabled.

current behavior: ok button is gray
fixed it.

update the expression listener.
verified in 2.6.0.v201004290630