Switches directive broke in 6.42

[erkyrath]

Switches "S";
[ Main;];

% ./inform-6.41 test.inf
Inform 6.41 (22nd July 2022)
line 1: Warning: Obsolete usage: the Switches directive is deprecated and may produce incorrect results. Use command-line arguments or header comments.

% ./inform-6.42 test.inf
Inform 6.42 (10th February 2024)
line 1: Error: Expected string of switches but found string "S"

It's deprecated but it's not supposed to be an error.