Embedded SQL - cast blank field to zeros

I've searched the archives for this and haven't been able to find an
answer. I inherited an SQLRPGLE program that reads (using SQL Fetch) an
old QS36F file and writes certain fields to another file. Unfortunately,
S/36 Environment still allows numeric fields to contain blanks (spaces).
When it tries to do a fetch on a record with a blank numeric field, SQL
quietly barfs on itself with status 22018, error -420. I've tried
explicit casting in various forms and none of them work. I've also added
and H-spec fixnbr(*zoned) which apparently has no effect on embedded SQL

Is there a simple way to get around this? I know I can do case logic for
each numeric field -

case
when substr(F00001,501,6) > '000000'
then substr(F00001,501,6)
else '000000'
end

But there are dozens of numeric fields in this file. And there are a
multitude of programs similar to this, waiting in the wings.

Any help would be greatly appreciated. I'm running out of aspirin.

TIA.

Timothy Adair