[birt-dev] CheckIn: Fix [Bugzilla] 128339:Data field is not cleaned out

["Xiong Zhang" <xiong.zhang@xxxxxxxxxxx>]

-Summary:
Data field is not cleaned out in _expression_ builder when change the image's data binding

- Bugzilla Bug (s) Resolved:
128339

- Description:
When a image bind to another dataset, the previous dataset should be cleaned out.


- Tests Description:

- Notes to Build Team:

- Notes to Developers:

- Notes to QA:

- Notes to Documentation:

- Files Added:

- Files Edited:

/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/editors/schematic/editparts/ImageEditPart.java
/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ImageBuilder.java