Bug 148626 [Regression]Can't fetch value from the filter of table/chart which inherites data from container
Steps: 1. create a table and bind a dataset in it 2. create another table/chart in the table detail/table group header 3. switch to the Filter tab in property editor 4. create a filter and select value in "<select value...>" combo 5. an error popuped up, "The expression value can't be retrieved"
chart/org.eclipse.birt.chart.reportitem.ui/src/org/eclipse/birt/chart/reportitem/ui/ReportDataServiceProvider.java
names[i] = handles[i].getName( );
		}
		return names;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.chart.ui.swt.interfaces.IDataServiceProvider#getAllStyleDisplayNames()
	 */
	public String[] getAllStyleDisplayNames( )
	{
		StyleHandle[] handles = getAllStyleHandles( );
		String[] names = new String[handles.length];
		for ( int i = 0; i < names.length; i++ )
		{
			names[i] = handles[i].getDisplayLabel( );
		}
		return names;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.chart.ui.interfaces.IDataServiceProvider#getCurrentStyle()
	 */
	public String getCurrentStyle( )
	{
		if ( itemHandle.getStyle( ) == null )
		{
			return null;
		}