Scripting a Field with multiple fields with Null values

Hi,

I'm attempting to use a script processor to add the sum of other fields into a total field, but some of the values are null. I know that I can use a "gsub" or "set" processors to set null values to 0, but the "gsub" processor only allows strings. I also know that I can create a Dynamic template to do the conversions as well. Can anyone tell me the easiest way to set "null" values found in any field to 0? I would use the null_value setting in my index, but the problem is that I'm trying to calculate a score before the document gets indexed.