fix(orm): preserve nested partial select on left join when first column is null (#1603)

[ElvinGts]

Fixes #1603
/claim #1603

Summary

Fixes an issue where mapResultRow improperly nullifies a nested partial-select object when the first selected field of a left-joined table evaluates to null, even if subsequent fields from the same table contain non-null values.

Root Cause

In mapResultRow (drizzle-orm/src/utils.ts), nullifyMap[objectName] stored the table name when encountering the first null column, but only cleared the nullify flag when encountering a field from a different table. Non-null values from the same table failed to reset the flag.

Changes

• Corrected the nullification guard in mapResultRow to ensure any non-null column value immediately clears the pending nullification.
• Preserves object structure when later fields in the same joined table have valid data.