Bug 153523 OK button in parameter dialog is enabled without default value in combo-box
Description: OK button in parameter dialog is enabled without default value in combo-box Steps to reproduce: 1. New a report parameter, combo-box. 2. Click New button, input abc as value, click OK 3. Set abc as default value and close Edit Parameter dialog. 4. New a data source and dataset 5. Edit the parameter, remove abc value and import values from dataset Expected result: OK button is disabled for there is no default value. Actual result: OK button is enabled.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
{
					inputParameter.setConcealValue( getProperty( CHECKBOX_DO_NOT_ECHO ) );
				}
			}
			else
			{
				inputParameter.setProperty( ScalarParameterHandle.CONCEAL_VALUE_PROP,
						null );
			}
			if ( needSort.isEnabled( ) )
			{
				if ( dirtyProperties.containsKey( CHECKBOX_SORT ) )
				{
					inputParameter.setFixedOrder( !getProperty( CHECKBOX_SORT ) );
				}
			}
			else
			{
				inputParameter.setProperty( ScalarParameterHandle.FIXED_ORDER_PROP,
						null );
			}
			
			if ( !isStatic( ) && !StringUtil.isBlank( listLimit.getText( ) ) )
			{
				try
				{
					inputParameter.setListlimit( Integer.parseInt( listLimit.getText( ) ) );
				}
				catch ( NumberFormatException ex )
				{