Unwanted spaces being placed in shapefile text fields by ArcGIS Desktop?

I have a table with a row Page_Number_N some of the rows have values and others just have a space. For example record 4 is just a space. Field values are Strings.

1
2
3

5

When I start an edit session and delete the space it deletes it. However, as soon as I save edits, the space in the data returns.

I have tried removing the space in the field calc without edit session turned on and the result is the same.

I need this record to equal "" ie. No spaces or null and I can't seem to get ArcGIS Desktop to cooperate.

Does anyone know how to fix this?