Bug 191430 [Regression] The table will binding to the data set if add a data binding to the data set [0001]
Description: The table will binding to the data set if add a data binding to the data set. Build number: 2.2.0.v20070607-0630 Steps to reproduce: 1. New a report with a data set. 2. New a table (not binding to the data set), add a data in one table cell. 3. Right click to change the data column, select the data set and one column. 4. Select the table and go to the binding page. Expected result: The table is binding to only one column. Actual result: The table is binding to the data set. Error log: N/A
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
* 
	 * @param str1
	 * @param str2
	 * @return
	 */
	public static boolean isSameString( String str1, String str2 )
	{
		if ( str1 == null && str2 == null )
		{
			return true;
		}
		if ( str1 != null && str1.equals( str2 ) )
		{
			return true;
		}
		return false;
	}
	/**
	 * Create a row expression base on a binding column name.
	 * 
	 * @param columnName
	 *            the column name
	 * @return the expression, or null if the column name is blank.
	 */
	public static String getColumnExpression( String columnName )
	{
		Assert.isNotNull( columnName );
		if ( StringUtil.isBlank( columnName ) )
		{
			return null;