Bug 141959 Changing data set didn't clean old column bindings
Steps to reproduce: 1.Add two data sets, "ds1" and "ds2" 2.Add a table, binding with "ds1". All "ds1" column bindings generate automatically, that's good 3.Change "ds1" to None Expected result: All "ds1" column bindings should be cleaned Actual result: All "ds1" column bindings are still there. If changing to "ds2", "ds2" column bindings will be added after them.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ColumnBindingDialog.java
if ( value != null )
				{
					for ( int i = 1; i < groups.length; i++ )
					{
						if ( value.equals( groups[i] ) )
						{
							return new Integer( i );
						}
					}
				}
				return new Integer( 0 );
			}
			if ( value == null )
			{
				value = ""; 
			}
			return value;
		}
		public void modify( Object element, String property, Object value )
		{
			if ( element instanceof Item )
			{
				element = ( (Item) element ).getData( );
			}
			try
			{
				if ( COLUMN_NAME.equals( property ) )
				{
					String newName = UIUtil.convertToModelString( (String) value,
							false );