Bug 167545 Copy a cascading parameter group and paste it to another parameter group causes an exception thrown
Steps to reproduce: 1.Copy a cascading parameter group using short cut key "Ctrl+x"/"Ctrl+c", or choosing context menu "Cut"/"Copy"; 2.Paste it to another parameter group using short cut key "Ctrl+v", or choosing context menu "Paste"; Expected result: The source one is pasted in the destination. Actual result: An exception thrown org.eclipse.birt.report.model.api.command.ContentException: The Cascading Parameter Group("Source") is not allowed in the slot (parameters) of Parameter Group("Destination").
UI/org.eclipse.birt.report.designer.core/src/org/eclipse/birt/report/designer/util/DEUtil.java
Object[] stylesArray = ( styles == null ? new Object[0]
				: styles.toArray( ) );
		if ( comparator != null )
		{
			Arrays.sort( stylesArray, comparator );
		}
		return Arrays.asList( stylesArray ).iterator( );
	}
	/**
	 * Checks if two strings have same value.
	 * 
	 * @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.
	 *