Bug 147852 [regression]Combo/listbox parameter doesn't work when put in parameter group
Description: Combo/listbox parameter doesn't work when put in parameter group Steps to reproduce: 1. New a prameter group 2. Insert a textbox parameter 3. Insert a combo/listbox parameter, input several values 4. Preview and select parameter values Expected result: Values can be selected Actual result: Once you selected a value from combo/listbox parameter list, the list would become empty.
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ScalarParameterBean.java
* @return whether parameter value allows blank.
	 */
	public boolean allowBlank( )
	{
		if ( parameter == null )
		{
			return true;
		}
		
		return parameter.allowBlank( );
	}
	
	/**
	 * Adapt to IScalarParameterDefn's allowNewValues( ).
	 * 
	 * @return whether parameter selection list allows new value.
	 */
	public boolean allowNewValues( )
	{
		if ( parameter == null )
		{
			return false;
		}
		
		return !parameter.mustMatch( );
	}
	/**
	 * Adapt to IScalarParameterDefn's isValueConcealed( ).
	 * 
	 * @return whether parameter value is concealed.