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
defaultValueChooser.select( 2 );
				}
				else
				{
					defaultValueChooser.setText( defaultValue );
				}
			}
			else if ( defaultValue != null )
			{
				defaultValueChooser.setText( defaultValue );
			}
			distinct.setSelection( !inputParameter.distinct( ) );
			String sortKey = inputParameter.getSortBy( );
			if ( sortKey == null
					|| sortKey.equals( DesignChoiceConstants.PARAM_SORT_VALUES_LABEL ) )
			{
				sortKeyChooser.setText( CHOICE_DISPLAY_TEXT );
			}
			else
			{
				sortKeyChooser.setText( CHOICE_VALUE_COLUMN );
			}
			if ( inputParameter.getSortDirection( ) == null )
			{
				sortDirectionChooser.setText( NONE_DISPLAY_TEXT );
			}
			else if ( inputParameter.getSortDirection( ).equals( DesignChoiceConstants.SORT_DIRECTION_ASC ) )
			{
				sortDirectionChooser.setText( CHOICE_ASCENDING );
			}