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
inputParameter.setCategory( formatCategroy );
			inputParameter.setPattern( formatPattern );
			if ( isStatic( )
					&& ( PARAM_CONTROL_COMBO.equals( getSelectedControlType( ) ) || DesignChoiceConstants.PARAM_CONTROL_RADIO_BUTTON.equals( getSelectedControlType( ) ) )
					&& !containValue( null, defaultValue, COLUMN_VALUE ) )
			{
				defaultValue = null;
			}
			
			if ( dirtyProperties.containsKey( CHECKBOX_HIDDEN ) )
			{
				inputParameter.setHidden( getProperty( CHECKBOX_HIDDEN ) );
			}
			if ( PARAM_CONTROL_LIST.equals( getSelectedControlType( ) )
					|| DesignChoiceConstants.PARAM_CONTROL_TEXT_BOX.equals( getSelectedControlType( ) ) )
			{
				if ( dirtyProperties.containsKey( CHECKBOX_ALLOW_BLANK ) )
				{
					inputParameter.setAllowBlank( getProperty( CHECKBOX_ALLOW_BLANK ) );
				}
				if ( dirtyProperties.containsKey( CHECKBOX_ALLOW_NULL ) )
				{
					inputParameter.setAllowNull( getProperty( CHECKBOX_ALLOW_NULL ) );
				}
			}
			else
			{
				inputParameter.setProperty( ScalarParameterHandle.ALLOW_BLANK_PROP,
						null );
				inputParameter.setProperty( ScalarParameterHandle.ALLOW_NULL_PROP,