[birt-dev] CheckIn:Fix bugzilla bug 147906 Creating a joint data set bas

["Mingxia Wu" <mwu@xxxxxxxxxxx>]

Title: CheckIn:Fix bugzilla bug 147906 Creating a joint data set based on 2 data sets from a library gives error

- Summary:
Fix bugzilla bug 147906 Creating a joint data set based on 2 data sets from a library gives error 

- Bugzilla Bug (s) Resolved:
147906

- Description:
The joint data set should allow no datasource existing. Delete the check on data source and add the check on data sets

- Tests Description:
Manual test

- Notes to Build Team:

- Notes to Developers:

- Notes to QA:  

- Notes to Documentation:  

- Files Edited:
/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/data/ui/dataset/JointDataSetPage.java
/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/actions/NewJointDataSetAction.java

- Files Added:

- Files Deleted