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.setProperty( ScalarParameterHandle.LIST_LIMIT_PROP,
						null );
			}
		}
		catch ( Exception e )
		{
			ExceptionHandler.handle( e );
			return;
		}
		setResult( inputParameter );
		super.okPressed( );
	}
	private void createLabel( Composite parent, String content )
	{
		Label label = new Label( parent, SWT.NONE );
		if ( content != null )
		{
			label.setText( content );
		}
		setLabelLayoutData( label );
	}
	private void setLabelLayoutData( Label label )
	{
		GridData gd = new GridData( );
		if ( label.getText( ).equals( LABEL_VALUES ) )
		{
			gd.verticalAlignment = GridData.BEGINNING;
		}
		label.setLayoutData( gd );