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
msgLineGridData.horizontalSpan = 2;
		errorMessageLine.setLayoutData( msgLineGridData );
	}
	/**
	 * Set the input of the dialog, which cannot be null
	 * 
	 * @param input
	 *            the input of the dialog, which cannot be null
	 */
	public void setInput( Object input )
	{
		Assert.isNotNull( input );
		Assert.isLegal( input instanceof ScalarParameterHandle );
		inputParameter = (ScalarParameterHandle) input;
	}
	protected boolean initDialog( )
	{
		Assert.isNotNull( inputParameter );
		nameEditor.setText( inputParameter.getName( ) );
		if ( !StringUtil.isBlank( inputParameter.getPromptText( ) ) )
		{
			promptTextEditor.setText( inputParameter.getPromptText( ) );
		}
		helpTextEditor.setText( UIUtil.convertToGUIString( inputParameter.getHelpText( ) ) );
		if ( inputParameter.getValueType( )
				.equals( DesignChoiceConstants.PARAM_VALUE_TYPE_STATIC ) )
		{
			staticRadio.setSelection( true );
			for ( Iterator iter = inputParameter.getPropertyHandle( ScalarParameterHandle.SELECTION_LIST_PROP )
					.iterator( ); iter.hasNext( ); )