Correct the default options if default invalid

The default value should be a list and have set the default to the new
"No Fancy Date Format" option.

src/app-utils/options.scm

@@ -1319,7 +1319,7 @@
   (define (def-value)
     (if (list? default-value)
         default-value
-        '(locale number #t "")))
+        (list 'unset 'number #t "")))
 
   (let* ((value (def-value))
          (value->string (lambda ()