locale.c: Free curlocales[j] before overwriting

The way to `curlocales[]` was handled in `Perl_init_i18nl10n' was a bit
fragile (in my opinion).

If one wasn't careful then it could lead to
- double free
- a (small) memory leak

With the current code there does not appear to be a way to trigger either
of those but it was to fragile for my liking.

By calling `Safefree` before overwriting the value the code becomes (imo) more
logical and the risk of the double free/memory leak disappears.

For much more details see GH #20002

locale.c

@@ -3541,6 +3541,7 @@ Perl_init_i18nl10n(pTHX_ int printwarn)
         if (! setlocale_failure) {
             unsigned int j;
             for (j = 0; j < NOMINAL_LC_ALL_INDEX; j++) {
+                Safefree(curlocales[j]);
                 curlocales[j] = setlocale_i(j, trial_locale);
                 if (! curlocales[j]) {
                     setlocale_failure = TRUE;
@@ -3576,9 +3577,6 @@ Perl_init_i18nl10n(pTHX_ int printwarn)
                     if (! curlocales[j]) {
                         PerlIO_printf(Perl_error_log, "\t%s\n", category_names[j]);
                     }
-                    else {
-                        Safefree(curlocales[j]);
-                    }
                 }
 
 #  endif /* LC_ALL */