[birt-dev]CheckIn: Fix Bugzilla Bug 158511 --- DataID.append() should pr

["Wei Zhao (Shang)" <wei.zhao@xxxxxxxxxxx>]

Title: [birt-dev]CheckIn: Fix Bugzilla Bug 158511 --- DataID.append() should process null dataset.

- Summary:
Do not call dataSet.append if dataSet is null in append method.

- Bugzilla Bug (s) Resolved:
Fix Bugzilla Bug 158511 --- DataID.append() should process null dataset.

- Description:
When dataSet was null, it will cause NPE  while calling dataSet.append.
Because if dataSet is null, we needn't call its append method. Fix it by not calling dataSet.append if dataSet is null.

- Tests Description  :
Manual Test

- Notes to Build Team:

- Notes to Developers:

- Notes to QA:  
 
- Notes to Documentation:  

- Files Edited:
"/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/DataID.java"

- Files Added:

- Files Deleted

-Wei Zhao( Shanghai )