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
}
		return str;
	}
	private boolean containValue( SelectionChoice selectedChoice,
			String newValue, String property )
	{
		for ( Iterator iter = choiceList.iterator( ); iter.hasNext( ); )
		{
			SelectionChoice choice = (SelectionChoice) iter.next( );
			if ( choice != selectedChoice )
			{
				String value = null;
				if ( COLUMN_VALUE.equals( property ) )
				{
					value = choice.getValue( );
					if ( isEqual( value, newValue ) )
					{
						return true;
					}
				}
				if ( COLUMN_DISPLAY_TEXT.equals( property ) )
				{
					value = choice.getLabel( );
					if ( value == null )
					{
						value = choice.getValue( );
					}
					if ( value == null )
					{
						value = LABEL_NULL;