Bugfix: inconsistency in c_base_error's s_false() and s_true() NULL value handling

Bugfix: inconsistency in c_base_error's s_false() and s_true() NULL value handling

The comments designate that when NULL is specified, no error should be assigned.
The previous behavior was instead creating a new, empty error.

The error classes also seem to accept NULL values, which will create an empty error array (clearing existing values).
By passing NULL instead of creating an error object makes the behavior consistent with other code.