Bug 182673 No default value error message prompts incorrectly
Steps to reproduce: 1. New a report parameter; 2. Choose control type as Combo; 3. Choose parameter as dynamic type; Expected result: As the isRequired is false by default, parameter's default value can be null value. There should be no error message about no default value prompt. Actual result; Error messages prompts
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
.getVisibleDataSets( )
				.iterator( ); iterator.hasNext( ); )
		{
			DataSetHandle DataSetHandle = (DataSetHandle) iterator.next( );
			dataSetList.add( DataSetHandle.getQualifiedName( ) );
		}
		if ( inputParameter.getDataSetName( ) != null
				&& !dataSetList.contains( inputParameter.getDataSetName( ) ) )
		{
			dataSetList.add( 0, inputParameter.getDataSetName( ) );
		}
		if ( oldList.length != dataSetList.size( ) )
		{
			dataSetChooser.setItems( (String[]) dataSetList.toArray( new String[]{} ) );
			if ( StringUtil.isBlank( selectedDataSetName ) )
			{
				dataSetChooser.select( 0 );
				refreshColumns( false );
			}
			else
			{
				dataSetChooser.setText( selectedDataSetName );
			}
		}
	}
	private DataSetHandle getDataSetHandle( )
	{
		return inputParameter.getModuleHandle( )
				.findDataSet( dataSetChooser.getText( ) );
	}