Bug 146796 Error message pop up if display text contain non-digital char when add next item
Description: In decimal type parameter creation,display type is "list box", Error message pop up if "display text" contain non-digital char when add next item. Steps: 1.Create a new decimal parameter 2.Set display type as "list box" 3.Input one item: value:1, display text:test 4.Input another item: Value:2 Actual result: error message pop up: The display text already exists! Expected result: Input item succussfully.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
}
		catch ( BirtException e )
		{
			
		}
		catch ( ParseException e )
		{
		}
		return string;
	}
	/**
	 * Check if the specified value is valid
	 * 
	 * @param value
	 *            the value to check
	 * @return Returns the error message if the input value is invalid,or null
	 *         if it is valid
	 */
	private String isValidValue( String value )
	{
		if ( canBeNull( ) )
		{
			if ( value == null || value.length( ) == 0 )
			{
				return null;
			}
		}
		else
		{
			if ( value == null || value.length( ) == 0 )