CSV Feeder Null Value Silent Defaulting in EL Expressions

Gatling feeder expression language evaluates column values through EL expressions; when a feeder column contains a null, the expression may silently default to an empty string, propagating unexpected request parameters without explicit indication.

This behavior varies by feeder implementation: a CSV feeder with missing rows treats the value as null, while a Map feeder accessed via ${column} may throw a ClassCastException depending on runtime type resolution. When such a null value is used in an assertion, the test fails without a descriptive message, complicating the identification of data-flow issues.

What are the exact conditions under which a CSV feeder silently converts a null column value to an empty string in an EL expression? Does accessing a null entry through a Map feeder consistently produce a ClassCastException, and under what type constraints? Is there a documented or reliable method to null-check a feeder column value within an EL expression, or does the syntax remain undocumented and version-dependent?