Bug 166315 Combo box doesn't allow blank when set string type in parameter editor
Combo box doesn't allow blank when set string type in parameter editor Steps to reproduce: 1.New a parameter, display type is Combo Box 2.Select data type as String Expected result: "Allow blank values" is enable. Actual result: "Allow blank values" is gray and can't be checked.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
if ( refresh )
			{
				refreshValueTable( );
			}
		}
	}
	private boolean canBeBlank( )
	{
		boolean canBeBlank = false;
		if ( PARAM_CONTROL_LIST.equals( getSelectedControlType( ) )
				|| DesignChoiceConstants.PARAM_CONTROL_TEXT_BOX.equals( getSelectedControlType( ) ) )
		{
			if ( dirtyProperties.containsKey( CHECKBOX_ALLOW_BLANK ) )
			{
				canBeBlank = ( (Boolean) dirtyProperties.get( CHECKBOX_ALLOW_BLANK ) ).booleanValue( );
			}
			else
			{
				canBeBlank = inputParameter.allowBlank( );
			}
		}
		return canBeBlank;
	}
	private boolean canBeNull( )
	{
		boolean canBeNull = false;
		if ( dirtyProperties.containsKey( CHECKBOX_ALLOW_NULL ) )
		{
			canBeNull = ( (Boolean) dirtyProperties.get( CHECKBOX_ALLOW_NULL ) ).booleanValue( );
		}