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
inputParameter.setMustMatch( false );
			}
			else if ( PARAM_CONTROL_LIST.equals( newControlType ) )
			{
				newControlType = DesignChoiceConstants.PARAM_CONTROL_LIST_BOX;
				
				inputParameter.setMustMatch( true );
			}
			else
			{
				inputParameter.setProperty( ScalarParameterHandle.MUCH_MATCH_PROP,
						null );
			}
			
			inputParameter.setControlType( newControlType );
			
			if ( DesignChoiceConstants.PARAM_TYPE_DATETIME.equals( getSelectedDataType( ) ) )
			{
				defaultValue = DEUtil.convertToXMLString( DataTypeUtil.toDate( defaultValue,
						ULocale.US ) );
			}
			inputParameter.setDefaultValue( defaultValue );
			
			inputParameter.setDataType( DATA_TYPE_CHOICE_SET.findChoiceByDisplayName( dataTypeChooser.getText( ) )
					.getName( ) );
			
			PropertyHandle selectionChioceList = inputParameter.getPropertyHandle( ScalarParameterHandle.SELECTION_LIST_PROP );
			selectionChioceList.setValue( null );
			if ( isStatic( ) )
			{